说明：
本文是在国内GMAT考生中广为流传的PREP语法笔记整理而成。这些PREP题目，包括了老PREP和新PREP中的各2套共493道题目。我们把这些题目，按20道题目一组，创建了25个练习册，方便大家先做后看。
注意：此部分解析为非官方、非专业老师整理的解析。
241. (GWD-9-Q39, OG12-131)
Over 75 percent of the energy produced in France derives from nuclear power, while in Germany it is just over 33 percent.
A. while in Germany it is just over 33 percent
B. compared to Germany, which uses just over 33 percent
C. whereas nuclear power accounts for just over 33 percent of the energy produced in Germany
D. whereas just over 33 percent of the energy comes from nuclear power in Germany
E. compared with the energy from nuclear power in Germany, where it is just over 33 percent
题目释义：Over 75 percent of the energy produced in France derives from nuclear power, whereas nuclear power accounts for just over 33 percent of the energy produced in Germany
考点：
逻辑意思（logical predication） 平行结构（parallelism）
1. whereas/while这种连词连接的比较成分不要求含义上绝对的平行，具体见prep 1-211。
2. 1) they, their, it都是完整指代，即指代包含了被指对象的所有修饰成分
**注意仅仅是修饰词，如：
In Japan elderly people are treated with far greater respect than they are in most Western countries.如果前面的elderly people没有其他修饰，后面时可以用they来指代的。
2) one和that，those是核心词指代。
3) that , one , it 的区别见补充说明。
3. 1) compared with直接跟在逗号后面可以修饰逗号前面名词短语的核心词：
Example：
In the United States, while the number of foreign-born residents and their children is higher than ever, the percentage of the population they represent is not; in 1910 this group made up 35 percent of the population, compared with 20 percent in 2000.
2) Compared with也可以修饰前面整个分句，compared with后面的名词与主语比较：
Example:
u Today, more than 43 percent of Californians under the age of eighteen are Hispanic, compared with about 35 percent a decade ago.
u In the United States, Fifty-two percent of high school graduates go on to college, compared with thirty-five percent in Canada and fifteen percent in Great Britain, Japan, and West Germany.
u One baby in four is now born to a mother aged thirty or older, compared with just one in six in 1975.
3) as compared to/with中as指代前面整句的核心含义：
A recent review of pay scales indicates that, on average, CEO's now earn 419 times the pay of blue-collar workers, as compared to 42 times their pay, the ratio in 1980.
选项分析：
A. it完整指代75 percent of the energy produced in France，意思错误；在比较成分前后都是句子的情况下，前面分句是主谓宾结构表达动作，后面分句是主系表结构表达状态，功能上不平行，错误
B. compared to比较不平行：75%和Germeny比较；33 percent所指代的事物不明确
C. Correct；前后都是主谓宾结构；介词短语充当地点状语前后对称，位置正确；比较了法国和德国各自的来自于核能的能量
D. 由于in Germany位置变成了修饰nuclear power，就变成了“在法国，超过33%的能量来自于德国生产的核能”；同时失去了比较的意味, 这个选项里用的whereas是没意义的。
E. 句式wordy；it指代不清
OG12-131解释：
Rhetorical construction; Logical predication
This sentence compares percentages and uses the prepositional phrases in France and in Germany to
distinguish the percentage of energy in each country coming from nuclear power. This information is most efficiently and clearly presented in two clauses joined by the conjunction whereas, which signifies a difference between the situations in the two countries. Each clause must identify what the percentage refers to—that is, the portion of the respective country’s energy that comes from nuclear power.
A While is somewhat ambiguous, since it might indicate simultaneity rather than contrast; the referent of it is ambiguous, raising questions about just what two things are being compared.
B This sentence compares 75 percent to Germany; it is not clear what 33 percent refers to.
C Correct. Th e two clauses joined by whereas indicate clearly that the comparison is between the diff erent percentages of energy coming from nuclear power.
D The use of the definite article the makes it seem as though the energy being referred to in this part of the sentence is that of France.
E This construction is wordy and unclear; the referent of it is ambiguous.
The correct answer is C.
补充说明：
that , one , it 的区别--aeoluseros:
I. it／one ／that三者均可用作代词, 指代前面提到的名词。一般说来, it指代同名同物; one与that则指代同名异物。
I have lost my umbrella; I'm looking for it. （该句中it就是指前面的my umbrella）
I have lost my umbrella; I think I must buy one. （one在该句中表泛指, 因为my umbrella已经丢了）
The umbrella you bought is cheaper than that I bought. （替代词that在该句中特指“the umbrella I bought”, 以区别“the umbrella you bought”）
II. one与that虽可用来指代同名异物, 但one为泛指, 相当于a／an＋名词; that为特指, 相当于the ＋名词。所以one所指代的名词的修饰语一般为 a／an ／some ／any; that所指代的名词的修饰语往往是the ／this ／that。
A chair made of steel is stronger than one made of wood. （该句中one可以换成a chair）
The water in the cup is hotter than that in the pot. （该句中that可以换成 the water）
III. one只能代替可数名词单数, 代替可数名词复数时用ones; that既可以代替不可数名词也可以代替可数名词单数, 代替可数名词复数时用 those。
I like this pen more than that one. （one代替可数名词单数pen）
There were a few young people and some older ones in the house. （ones代替可数名词复数people）
Mary's handwriting is far better than that of Peter. （that代替不可数名词 handwriting）
These pictures are more beautiful than those. （those代替可数名词复数 pictures）
IV. one既可代替事物, 也可代替人, that只能代替事物而不能代替人。有时可以用the one或the ones代替that或those。
The one ／That on the table is mine. （该句中The one代替事物, 并且也可以用That）
He is the teacher, the one who is loved by the students. （该句中the one代替人, 不能用that）
He advised the farmers to choose the best seed-heads, the ones ／those that had the best color. （该句中the ones代替事物, 并且也可以用those）
V. one一般有前置修饰语, 有时也可有后置修饰语或不用修饰语。而 that不能有前置修饰语, 但可有后置修饰语。
Cook was a strict but good captain, one who took good care of his sailors.
The water in the well is cleaner than that in the river.
VI. it可以替代句中的不定式或从句等, 充当形式主语或形式宾语。one与that均无此用法。
It is known to everybody that the moon travels around the earth once every month.
I found it hard to get on with her.
VII. it与that均可以替代上文全句的内容或部分内容, 而one ／ones则不可以（本条为日常语法中常用，而GMAT中it与that无法指代上文全句，）。
He has saved my life; I'll never forget it. （it代替第一分句）
Tom is painting his house. I am told he does it every four years. （it代替前面分句的部分内容painting his house）
Let's say we meet here at three o'clock. That ought to give you
242. (GWD-1-Q38)
Retail sales rose 8/10 of 1 percent in August, intensifying expectations that personal spending in the July-September quarter more than doubled that of the 1.4 percent growth rate in personal spending for the previous quarter.
A. that personal spending in the July-September quarter more than doubled that of
B. that personal spending in the July-September quarter would more than double
C. of personal spending in the July-September quarter, that it more than doubled
D. of personal spending in the July-September quarter more than doubling that of
E. of personal spending in the July-September quarter, that it would more than double that of
题目释义：…, intensifying expectation that PS in J-S quarter would more than double the 1.4 percent growth rate in PS for the previous quarter.
考点：
动词形式（Verb form）;逻辑含义（Logical predication）
1. expectations表达将来预测的含义，用同位语从句更能体现时态的精准，而且如果用了of从属结构显得冗长累赘，句意表达不清。
2. more than double the 1.4 percent growth rate，其中double是动词，more than是副词。
3. 对于more than doubled或is more than doubled的区分技巧：把more than脱去不看，doubled是一般过去时，而is doubled是被动语态
选项分析：
A. that跟在expectations后面表示具体内容；expectations的内容没有实现，不能用过去时；that没有指代。
B. correct；Would在这里表示expectation的内容没有实现。
C. 整个句式awkward，that为同位语从句引导词与of平行共同修饰expectations，其实没有必要先说一遍topic再接着详述，像B一样直接详述即可；doubled时态错误
D. Of短语无法明确表明expectations的核心内容，应该用同位语从句
E. 句式awkward错误同C
OG12-16的解释：
Verb form; Logical predication
The sentence explains the expectations that resulted from a past retail sales trend. Since expectations look to the future but are not yet realized, the relative clause explaining these expectations should be conditional, employing the auxiliary verb would.
A The simple past-tense verb form does not express the forward-looking sense of expectations.
B Correct. By using the verb would double, this concise sentence indicates that the expectation has not yet been realized.
C This construction is awkward, announcing the topic (personal spending) and then elaborating in a relative clause that restates this topic as it.
D Although this option is not technically wrong, it is less clear and graceful than B.
E Like option C, this sentence is awkward and unnecessarily wordy, announcing the topic and then using an additional clause to elaborate on it.
补充说明：
限制性定语从句和非限制性定语从句--from海词
一，限制性定语从句：
限制性定语从句对先行词起限制、修饰的作用，关系代词有that,which,whom,who,whose以及关系副词when,where等，没有明显的逗号把从句与主语分开，表达的意思为被修饰词的一个定语。
例句：
Do you know the professor who is speaking at the meeting?
Where is the book which I bought this morning?
二，非限制性定语从句：
作用相当于一种插入语或者对先行词的一种解释，和先行词之间只有比较松散的关系，文字中常常用逗号将其与主句分开，用法其实与限制性定语从句极为相似，只是不能用that做修饰词。
例句：
This letter is from his parents, who are working in Tibet.
Englishi is an important subject, which every students should study well.
The building, in front of which sat a boy, was a school.
243. (GWD-10-Q8)
Sulfur dioxide, a major contributor to acid rain, is an especially serious pollutant because it diminishes the respiratory system's ability to deal with all other pollutants.
A. an especially serious pollutant because it diminishes the respiratory system's ability to deal
B. an especially serious pollutant because of diminishing the respiratory system's capability of dealing
C. an especially serious pollutant because it diminishes the capability of the respiratory system in dealing
D. a specially serious pollutant because it diminishes the capability of the respiratory system to deal
E. a specially serious pollutant because of diminishing the respiratory system's ability to deal
题目释义：Sulfur dioxide, … , is…pollutant because it diminishes…ability to deal with…
考点：
习惯用语（idiom） 句子结构（grammatical construction）
1. capability to do；GMAT认为capability of X-ing/in X-ing是wordy/awkward的。
2. ability：sb's ability to do sth或ability of sb/sth to do sth
3. capability to do不如ability to do简洁，但不可就此判错。
选项分析：
A. Correct；ability to deal使用简洁；respiratory system's ability可以
B. because of后结构复杂，awkward（because of后面如果跟动名词则一般是累赘的）；capability of dealing不够简洁
C. in dealing有做状语修饰整个从句的歧义，含义变为Sulfur dioxide在dealing with的时候减少了respiratory system的能力，而不是原义想要表达的，减少了respiratory system的deal with…的能力；capability如果后面要加in doing,最好紧跟capability，避免歧义
D. especially强调严重性，specially强调特殊性，根据原义，选especially；of the respiratory system的插入，导致to deal可以修饰动词diminish，歧义
E. especially强调严重性，specially强调特殊性，根据原义，选especially； because of错误同B。
补充说明：
1. specially 和especially区别（记住这种小点，有益于快速解题）
Especially is most often used to emphasize something, or to say that something is more worth mentioning or more important than the other things you are talking about: It can be especially difficult for drivers to see cyclists at night. | The town is especially crowded in the summer (=much more than in winter). I hate interruptions, especially when I'm trying to work (=I do not mind as much at other times).
Specially is usually used when you do something that is different from what you usually do for a particular purpose. It is often used with the passive form of a verb: a specially made/designed/adapted etc car | I bought it specially for you
即：
especially强调严重性，specially强调特殊性！
especially是表示程度
specially表示特殊
2. capability和ability区别：ability to do和capability to do区别，在强调某人/物天生具有某种能力用ability好，capability可能强调的是能不能做某事（跟天生没什么关系），如government'capability或transport system's capability等。
1) If we don't take great care, SARS could become established in the poorest nations - places like Burundi, Nigera or Malawi - which have neither the high-tech capability of Toronto nor the totalitarian muscle of China to contain it
2) capability of sth. to be done表一种属性, 非一种主动的能力。
3) capability (of sth.）to do/of doing.
3. sth’s ability可用在无生命主体:
Additional evidence was provided by negative findings: drugs called adrenergic antagonists, which block peripheral adrenaline receptors, disrupted adrenaline’s ability to regulate memory but did not affect memory enhancements produced by glucose that was not stimulated by adrenaline.
244. (GWD-10-Q39)
In Japan, a government advisory committee called for the breakup of Nippon Telephone and Telegraph Company, the largest telephone company in the world, so it would be two local phone companies and one long-distance provider.
A. In Japan, a government advisory committee called for the breakup of Nippon Telephone and Telegraph Company, the largest telephone company in the world, so it would be
B. The breakup of the world's largest telephone company, Nippon Telephone and Telegraph Company, was called for by a government advisory committee in Japan, so it would be
C. A government advisory committee in Japan called for the breakup of Nippon Telephone and Telegraph Company, the world's largest telephone company, into
D. The breakup of Nippon Telephone and Telegraph Company, the world's largest telephone company, was called for by a government advisory committee in Japan, so it would be
E. Called for by a government advisory committee, the breakup of Nippon Telephone and Telegraph Company in Japan, the world's largest telephone company, was to be into
题目释义：A government advisory committee called for sth into…
考点：
逻辑意思（logical predication） 句子结构（grammatical construction）
1. 主从句的主语对位指代，即当从句的主语是代词时，往往指代主句的主语—但也不绝对。
2. Call for：叫(某人)来；要求，需要
3. 同位语修饰名词词组A of BG是不一定是修饰其中的核心词，可能就近修饰。
选项分析：
A. so it would be里的it指代歧义，本身应指代the largest telephone company，但是这里指代了主语a government advisory committee，错误
B. it指代了breakup错误； the world's largest telephone company是describtion，Nippon Telephone and Telegraph Company才是主体，应该用前者作为插入语修饰；没有特殊原因，没有必要用被动语态，反而不简洁。
C. correct；“,the world’s largest telephone company,”做插入语。
D. it的指代错误同B；没有特殊原因，没有必要用被动语态，反而不简洁。
E. “,the world’s largest telephone company,”同位语被in Japan隔开没有紧接其修饰的对象，错误；was to be into表达awkward。
245. (GWD-18-Q11)
In no other historical sighting did Halley's comet cause such a worldwide sensation as did its return in 1910–1911.
A. did its return in 1910–1911
B. had its 1910–1911 return
C. in its return of 1910–1911
D. its return of 1910–1911 did
E. its return in 1910–1911
题目释义：In no other sighting did HC cause such a sensation as in its return of 1910-1911
考点：
比较结构（comparison）
1. an event of + 年份，正确表达。
2. 状语的比较。从no other即看出比较的是状语。
选项分析：
A. 比较双方不对等：HC和its return
B. 比较双方不对等：HC和its return；助动词had错误，要用一般过去时
C. Correct；原句可还原为Halley 's comet did cause(caused) such a worldwide sensation in no other historical sighting as in its return of 1910-1911.相当于状语的对比：in no other historical sighting和in its return of 1910-1911的对比，比较结构中的内容是：”such a worldwide sensation in no other historical sighting as in its return of 1910-1911”，后面部分省略的是a world wide sensation；its return of 1910-1911它在1910-1911的回归，介词用of很常见，当然用in也可以
D. 比较双方不对等：HC和its return
E. 比较对象不对等：介词短语In no other historical sighting和名词短语its return in 1910–1911对比
补充说明：
1. 本题倒装+比较
Halley's comet did not cause such a worldwide sensation in other historical sighting as (a world wide sensation) in its return of 1910–1911
2. OG12-138解释：
Parallelism; Verb form; Logical predication
The single subject of this sentence is Halley’s Comet, and its single verb phrase is did cause. The comparison presented by the sentence is between adverbial phrases describing times when the comet was seen. Grammatically, the items being compared are parallel prepositional phrases beginning with the preposition in: in no other sighting and in its return in 1910–1911. This is the clearest, most economical way of presenting the information. The options that introduce a second verb (did or had) violate the parallelism and introduce a comparison between the comet itself (subject of the verb did cause) and the comet’s return (subject of the verb did or had).
A This sentence implies a comparison between the comet and its return.
B This sentence implies a comparison between the comet and its return; had is the wrong auxiliary verb form because it must be followed by caused instead of cause.
C Correct. The parallel prepositional phrases in this sentence correctly compare times when the comet was sighted.
D This sentence implies a comparison between the comet and its return.
E This sentence violates parallelism, implying a comparison between a prepositional phrase and a noun phrase.
Th e correct answer is C.
246. (GWD-9-Q27)
Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planetwide destruction.
A. and, if it strikes Earth, it can do tremendous damage to part of the planet but
B. and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would
C. and that, if it were to strike Earth, could do tremendous damage to part of the planet but would
D. and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would
E. and that, if it strikes Earth, it could experience a tremendous amount of damage but
题目释义：Scientists have identified an asteroid that is… and that, if it were to do sth., could do…but would not cause…
考点：
平行结构（parallelism） 句子结构（grammatical construction）
1. 虚拟语气的几种形式再重复：
If + Present , future 'if X happens , Y will happen'
If + past, would /could + verb
'if X happened , Y would happen'
'if X were to happen , Y would happen'
If + past perfect , would/could + have + verb
2. 指代问题。
选项分析：
A. strikes用了现在时，没有体现出假设的语气，同样can也不对，it并没有发生，所以只能could，But后面同样需要有情态动词，could/would。
B. if和but后面的it都指代part of the planet，两个都指代错误；if条件句里的虚拟语气谓语形式错误，表示可能与将来事件相反，应该用“动词过去式(be用were)，should + 动词原形(should在此无实际含义)或者were to + 动词原形”。
C. correct；定语从句的平行。
D. do part of the planet tremendous damage表达awkward,易有歧义，是理解成do part of （the planet tremendous damage）；it多余，应和前面can平行。It应指代asteroid, 但结构上却和前面一致，指代了earth，错。
E. 没有体现出假设的语气，strikes用了现在时；but后没有情态动词，表达不出假设的语气；两个主从对位的it从逻辑上说指代了不同的东西，错误；有了前面that关系代词做主语，it could中的it多余，定语从句已经有主语that。
247. (GWD-3-Q39)
Minivans carry as many as seven passengers and, compared with most sport utility vehicles, cost less, get better gas mileage, allow passengers to get in and out more easily, and have a smoother ride.
A. Minivans carry as many as seven passengers and, compared with most sport utility vehicles, cost less,
B. Minivans, which carry as many as seven passengers, compared with most sport utility vehicles, they cost less,
C. Minivans carry as many as seven passengers, in comparison with most sport utility vehicles, and have a lower cost, they
D. Minivans, carrying as many as seven passengers, compared with most sport utility vehicles, cost less,
E. Minivans, which carry as many as seven passengers, compared with most sport utility vehicles the cost is lower, and they
题目释义：Minivans carry…and, [compared with…, cost…, get…, allow…, and have….]
...V1 and，插入状语，V2...
考点：
平行结构（parallelism） 逻辑意思（logical predication）
1. 按照逻辑意思可以发现，动作carry和后面几个动作并不平行。这个句子的逻辑关系是，“Carry”这个动作没有参加“compared”，而是自成一个层次，而另外四个动词是“compared”的项目，它们另外组成了一连串的动词平行结构。故而A中的第一个“and”是必要的。
2. compared with用法见prep1-241
选项分析：
A. Correct；carry和后面的四个动作是大平行，cost，get，allow and have是小平行；and后面省略了主语。
B. Minivan和they双重主语，错误；compared with修饰对象成了前面的定语从句。
C. Run-on sentence，两套主谓宾结构；打破了原来逻辑含义合理的各动词平行结构。
D. 曾经的争议选项；compared with结构有修饰前面的carrying as many as seven passengers的歧义，squinting modifier。
E. 前半个分句有两个主语Minivans和the cost；Minivans, which carry as many as seven passengers成了悬垂结构；打破了原先逻辑含义合理的各动词平行结构。
248. (GWD-9-Q32)
The United States minted about 857 million silver-colored “Susan B. Anthony” dollars between 1979 and 1981, but the coin proved unpopular because it looked and felt too much like a quarter.
A. The United States minted about 857 million silver-colored “Susan B. Anthony” dollars between 1979 and 1981, but the coin
B. About 857 million silver-colored “Susan B. Anthony” dollars were minted as coins in the United States between 1979 and 1981 but
C. About 857 million silver-colored “Susan B. Anthony” dollars that were minted between 1979 and 1981 in the United States
D. About 857 million silver-colored “Susan B. Anthony” dollars that the United States minted between 1979 and 1981
E. Between 1979 and 1981 the United States minted about 857 million silver-colored “Susan B. Anthony” dollars, which
题目释义：The US minted about # dollars between 1979 and 1981, but the coin proved unpopular because it …
考点：
逻辑意思（logical predication） 句子结构（grammatical construction）
1. 未划线部分的代词是关注重点之一。
选项分析：
A. Correct；这里的between 1979 and 1981做时间状语修饰minted。
B. 未划线部分的it无指代，从该it看出but后面要加上一个单数名词做主语与状语从句的it对位；were minted被动语态不如主动语态简洁。
C. 未划线部分的it无指代；were minted被动语态不如主动语态简洁。
D. 未划线部分的it无指代；dollars后面的that多余，关系代词在定从中做宾语可以省略。
E. which指代dollars，使得it也指代dollars，单复数不一致错误。
249. (GWD-10-Q36) (GWD-11-19)
In Hungary, as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in middle management and light industry.
A. as in much of Eastern Europe, an overwhelming proportion of women work, many of which are in
B. as with much of Eastern Europe, an overwhelming proportion of women works, many in
C. as in much of Eastern Europe, an overwhelming proportion of women work, many of them in
D. like much of Eastern Europe, an overwhelming proportion of women works, and many are
E. like much of Eastern Europe, an overwhelming proportion of women work, many are in
题目释义：In H, as in much of EE, an overwhelming proportion of women work, many of them in middle management and light industy.
考点：
比较结构（comparison） 句子结构（grammatical construction）
1. as比较结构参考prep1-212
2. 使用like比较结构要确定两点：
1) like后面接的是名词，不能接介词短语或者句子等等。
2) like后面接的名词是在与紧随句子/分句的主语做比较。
3. "an overwhelming proportion of ..."是一个数量表达，逻辑上本身虽然是单数，但是语法上却视为复数，，因为它所代表的women是复数的，还有很多类似的表达比如percentages, proportions, fractions等。
选项分析：
A. Which和that都只能指代物，不能指代人。
B. as with比较不对称，错误；works单复数错误，要用work。
C. correct；them指代women，同位语后置；这里的as的比较对象平行。
D. an overwhelming proportion of women和much of Eastern Europe不能比较；works单复数形式错误；。
E. an overwhelming proportion of women和much of Eastern Europe不能比较；逗号不能连接俩个句子，中间需要有连词，run-on sentence。
250. (GWD30-Q29)
Researchers agreed that the study of new treatments for heart attack patients was extremely important but more research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than the balloon procedure by itself.
A. more research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than
B. more research was needed for determining whether or not balloon angioplasty preceded by ultrasound is any better for heart attack patients than is
C. that more research was needed to determine whether balloon angioplasty preceded by ultrasound is any better for heart attack patients than
D. that more research was needed to determine that balloon angioplasty preceded with ultrasound was any better for heart attack patients than
E. that more research was needed for determining that balloon angioplasty preceded by ultrasound is or is not any better for heart attack patients than is
题目释义：Researchers agreed that … was … but that … more research was needed to determine whether A is better for C than B.
考点：
平行结构（parallelism） 逻辑意思（logical predication） 习惯用语（idiom）
1. agree that…but that…，宾语从句的平行that不能省，使句子更加清晰。
2. need做实意动词的用法是：
need (sb.) to do sth；
need sth for sth；
sth needs n./doing/to be done(接名词性成分)；
3. whether or not的使用：
在引导宾从的时候只能够用whether，而不能加or not，否则累赘；
在引导状从的时候必须加上or not，即whether or not。
4. precede的惯用搭配是：A preceded by B（意思为B先进，然后A进）。
选项分析：
A. but后没有that，错误；”that…was or was not” wordy不如直接用whether；preceded with错误。
B. but后应补出that平行；whether or not累赘，直接用whether即可；仅仅是主语的比较，be动词is应该省略，省略is不会产生heart attack patients与the balloon procedure比较的歧义，如果两者要比较则必须后者也要补出介词for；need for doing不如need to do明确动作趋向。
C. correct；“同意A确实很不错了，但是也同意还是需要做B的”，逻辑没有问题；is用现在时没有问题，determine的内容如果现在还未最终决定下来时，is用现在时成立
D. determine that..."表示"确定/判定"己有结果，要用determine whether来表示结果未确定；preceded with错误；determine的内容发生在主句agree之后，所以应该用agree向后推移的时态：一般现在时is，而不能用一般过去时was。
E. need用法错误。That…is or is not是wordy。Than后面的is可以省略。
补充说明：
1. 一般的介词只能接疑问词引导的宾语从句，不能接that引导的宾语从句。但是but that=except that；in that=because(还是有不同) 这三个介词+that从句属于例外，约定俗成的用法。-----from 白勇语法
2. whether表示列举时候的用法：whether A, B, or C.
251. (GWD-1-Q29)
Faulty voting equipment, confusing ballots, voter error, and problems at polling places have been cited by a new study of the 2000 United States presidential election, which estimated that they did not count 4 million to 6 million of the 100 million votes cast.
A. Faulty voting equipment, confusing ballots, voter error, and problems at polling places have been cited by a new study of the 2000 United States presidential election, which estimated that they did not count 4 million to 6 million of the 100 million votes cast.
B. Citing faulty voting equipment, confusing ballots, voter error, and problems at polling places, a new study of the 2000 United States presidential election has estimated that 4 million to 6 million of the 100 million votes cast were not counted.
C. Citing faulty voting equipment, confusing ballots, voter error, and problems at polling places, 4 million to 6 million of the 100 million votes cast were not counted in the 2000 United States presidential election, a new study estimates.
D. A new study has cited faulty voting equipment, confusing ballots, voter error, and problems at polling places in estimating that 4 million to 6 million of the 100 million votes that were cast had not been counted in the 2000 United States presidential election.
E. A new study of the 2000 United States presidential election, citing faulty voting equipment, confusing ballots, voter error, and problems at polling places, has estimated 4 million to 6 million votes had not been counted of the 100 million votes cast.
题目释义：Citing A, B, C, and D, a study of sth. has estimated that…
考点：
逻辑意思（logical predication） 句子结构（grammatical construction）
1. --ing分词作句首，逻辑主语等于主语。
2. 所谓的“原句”，“合理重心”，都是根据逻辑意思判断的。特别对于长句子，能够在读题时迅速判断合理重心，是加快做题速度、提高正确率的第一利刃。
3. estimate的固定用法：
estimate (that)（不需加原V）
estimate + N + to be N(adj) (prep 2-51)
estimate + N + at/to be +数量词
*：Manhattan中认为估价的话要用to be，
比如RIGHT: She ESTIMATES the cost TO BE ten dollars.
WRONG: She ESTIMATES the cost AT ten dollars.
如：40 to 44 million years是时间概念，要用estimated to be 40 to 44 million years old.
选项分析：
A. 句子合理重心应该是结论为主句，达成结论的动作过程为辅，所以主从颠倒；定语从句中的they无所指。
B. Correct；Citing在句首，a new study是逻辑主语也是主语；句子重心合理。
C. citing逻辑主语错误，同时致使本应该是核心成分的a new study estimates成了插入语；estimates用现在完成时或者一般过去时问题都不大。
D. 句子重心错误；votes that were cast累赘，因为时态一致，可以省略that were；had been过去完成时错误，没有时间对比说明count这个动作发生在过去的过去(即便count是个瞬间动词，但是在否定句中瞬间动词也可以和表示一段时间的状语、连词连用，而是用完成时态)。
E. had not been时态错误；主谓相隔太远不好；复杂的句式estimate后面补出that更好。
252. (GWD7-Q1)
Although producer prices rose at an unexpectedly steep rate in September, analysts said that the increase resulted mostly from temporary factors and not necessarily foreshadowing that there would be a resurgence of inflation.
A. factors and not necessarily foreshadowing that there would be
B. factors and not necessarily that it foreshadowed
C. factors and did not necessarily foreshadow
D. factors, while not necessarily a foreshadowing of
E. factors, while it did not necessarily foreshadow that there would be
题目释义：Although…rose…, analyst said that the increase resulted mostly from temporary factors and did not necessarily foreshadow sth.
考点：
平行（parallellism） 逻辑意思（logical perdication）
1. 平行中后面部分省略的东西必须前面有重复的，使省略点能够补出。
2. 状语从句省略的形式：
1) 正确形式: 表示时间/条件/转折/让步的连词(when/while/if/unless/although/even though/even if) + 形容词短语/-ing短语/-ed短语
*：(逻辑主语等于句子主语) (所以when a child/ when children是错的； if + n.也是错的)
2) 错误形式: 表示时间/条件/转折的连词 + 介词短语/名词短语 (although just inside the orbit of Jupiter是错的)(OG10-69)
3) 特殊情况:once可以加介词短语/名词短语; whatever可以加名词短语
选项分析：
A. and前后resulted和forshadowing不平行；foreshadow that there would be不如直接forshadow + noun简洁。
B． 平行错误同A；平行的后半部分没有谓语，necessarily没有修饰对象。
C． Correct。
D． 前后句没有转折对比或者让步的含义，不该用while连接；while引导的状语从句省略错误；a foreshadowing of累赘。
E． there would be错误同A；while的错误同D。
253. (GWD 4-Q13)
A leading figure in the Scottish enlightenment, Adam Smith's two major books are to democratic capitalism what Marx's Das Kapital is to socialism.
A. Adam Smith's two major books are to democratic capitalism what
B. Adam Smith's two major books are to democratic capitalism like
C. Adam Smith's two major books are to democratic capitalism just as
D. Adam Smith wrote two major books that are to democratic capitalism similar to
E. Adam Smith wrote two major books that are to democratic capitalism what
题目释义：A figure, Adam wrote two books that are to DC what Marx’s DK is to socialism.
考点：
句子结构（grammatical construction） 习惯用语（idiom） 逻辑意思（logical predication）
1. a leading figure同位语修饰对象应该是人。
2. A is to B what C is to D，其中what近似just as,意为“恰像，犹如，好比”用作连词,引导比较状语从句。
选项分析：
A. 同位语修饰对象错误，修饰成了书。
B. 同位语修饰对象错误；like后面不能加主谓结构。
C. 同位语修饰对象错误。
D. similar to是介词短语后面只接名词，不能接句子。
E. correct；定语从句中的结构即A is to B what C is to D。
补充说明：
Due to，similar to，differing from等有形容词性质的介词，GMAT中一般不能出现在句首。
254. (GWD-29-Q36)
Section 301 of the 1988 Omnibus Trade and Competitiveness Act enables the United States Trade Representative to single out a country as an unfair trader, begin trade negotiations with that country, and, if the negotiations do not conclude by the United States government's being satisfied, to impose sanctions.
A. by the United States government's being satisfied, to impose
B. by the United States government's satisfaction, impose
C. with the United States government's being satisfied, imposing
D. to the United States government's satisfaction, impose
E. to the United States government's satisfaction, imposing
题目释义：… enables the USTR to single out..., begin...and, if…, impose...
考点：
平行结构（parallelism） 习惯用语（idiom）
1. do (sth.) to one’s satisfaction固定搭配，做某事以使人达到满意的程度。
2. conclude的固定搭配：
(1) conclude by doing sth./ conclude with sth.：以……结束，借此后面接的是结束的方式、行为
She concluded by saying she was proud to be from Salford.
Each chapter concludes with a short summary.
(2) conclude to ：达成……而结束
*:conclude可以做及物动词也可以做不及物动词
选项分析：
A. by one’s being satisfied累赘，固定习语搭配错误；Impose前不需要to，平行的是begin和impose。
B. by one’s satisfaction错误。
C. with one’s being satisfied错误；Imposing与begin不平行
D. correct；本题的conclude是不及物动词，后面跟的不是某个具体的方式，而是某个结果、效果，不应该用conclude by/with，所以A,B,C就直接排除了。
E. imposing平行错误。
255. (GWD-12-Q19)
Heavy commitment by an executive to a course of action, especially if it has worked well in the past, makes it likely to miss signs of incipient trouble or misinterpret them when they do appear.
A. Heavy commitment by an executive to a course of action, especially if it has worked well in the past, makes it likely to miss signs of incipient trouble or misinterpret them when they do appear.
B. An executive who is heavily committed to a course of action, especially one that worked well in the past, makes missing signs of incipient trouble or misinterpreting ones likely when they do appear.
C. An executive who is heavily committed to a course of action is likely to miss or misinterpret signs of incipient trouble when they do appear, especially if it has worked well in the past.
D. Executives’ being heavily committed to a course of action, especially if it has worked well in the past, makes them likely to miss signs of incipient trouble or misinterpreting them when they do appear.
E. Being heavily committed to a course of action, especially one that has worked well in the past, is likely to make an executive miss signs of incipient trouble or misinterpret them when they do appear.
题目释义：Being heavily committed to a course of action, especially one that…, is likely to make…when they…
过于专注某个做法，特别是某个过去一直挺有效的做法，很可能会使主管发现不了初期的故障信号或者当信号出现时错误地理解他们。
考点：
逻辑意思（logical predication） 句子结构（grammatical construction）
1. one是核心词指代，且为泛指。
2. 句式结构“行为一”导致“行为二”也是一种大平行。
3. a course of action 行动/运行/执行过程
选项分析：
A. commitment不如committed好，因为后面miss signs or misinterpret是动作，前面也是动作更加对称(大平行)；miss和misinterpret的行为者不清楚，至少要改为"makes it likely that the executive will miss..."才行；两个it距离过于接近，使得后面一个it让人理解起来有些模糊：是和前一个it指代一致，还是做形式宾语指代后面的to miss signs of …并不清晰。
B. 句子表达的含义是“经理使得missing signs和misinterpreting ones more likely”，是谁missing signs和misinterpreting不清楚；第一个one就近指代a course of action没问题(相当于同位语，后接同位语从句)；第二个ones指代的是signs，而不是signs of incipient trouble(one是核心词指代，且为泛指)；when they do appear的修饰对象错误，应该直接修饰misinterpreting，现在却成了整个句子的时间状语修饰了makes，且they无所指。
C. when they do appear修饰了平行的动词miss or misinterpret不合逻辑，明明miss了还do appear矛盾；especially if it has worked well in the past远离它修饰的course of action，使得it离所指的a course of action太远不好。
D. 而且Executives' being heavily committed to a course of action累赘； to miss和misinterpreting不平行；第一个them很明显是指代executives不会指代signs没有问题，因为一个作为misinterpret的主语(executives/第一个them)，一个作为misinterpret的宾语(signs/第二个them)；第三个they逻辑上就近与前一个them所指一致，所以没什么问题。
E. Correct；Being 强调是一个动作， gerund phrase 做主语；由于 a course of action 是泛指，后面应该用 One 指代而不是 it 更为合适； has worked well in the past ， in the past 完成时和过去时都可以用，因为 Past 可以是过去的一瞬间。
补充说明：
1. 关于秒杀：其实本题可以秒杀，越是长句子越容易秒杀----所谓秒杀就是从某一个判题点出发瞬间排除其他所有的选项，长句子往往可以通过理解了句子的各部分含义后，重组出自认为句子重心、含义，最合理的句子，通过4-1 split得出唯一的正确选项；如本题，只要看出最合理的意思是“非常遵从过去的行为”使得“经理犯错”（行为一导致行为二），就可以迅速建立答案倾向为E，时间不够马上选
256. (T-4-Q1 TS-7-41)
Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools.
A. when it is known that humans made
B. at which it is known that humans had made
C. at which humans are known to have made
D. that humans are known to be making (C)
E. of humans who were known to make
题目释义：Scientists have dated A found in B to # years ago, pushing back by # years the earliest date at which humans are known to have made.
考点：
1. be known to have done sth的问题：当be known 和 do sth的发生的时间一致时，用be known to do sth；而do sth发生在be known之前时，则要用be known to have done sth。
1. 大全748：...few people are known to have recovered from the disease once the clinical symptoms have appeared.
2. 大全849：...few people have been known to taste it for the first time without requesting more.
3. og49：......satellites now known to orbit the distant planet.
*：事实上在看这两个结构时，可以把be known to这个类似助动词的成分去掉；由于跟在be known to后面的动词要用原型，所以去掉be known to以后就可以单纯地比较have done和do，have done所表示的发生时间比do所表示的发生时间要早，如果事件发生在过去就用have done，发生在现在就用do。同时如果be known to do/have done sth后面接状语那么修饰的是do/have done，而不是known.
2. date to/at区分
1) date….to 可追溯sth到...几年，强调发生的时间点，后面是ago
2) date….at 年代判定、鉴别/年份有….年之久，强调发生到现在经过的时间有多长，后面是old
*：具体见后面补充说明。
选项分析：
A. 关系代词用when和at which都是可以的；此选项表达的意思是A fact is known at the earliest date，逻辑含义错误。
B. at which it is known表达的意思是A fact is known at the earliest date，逻辑含义错误；主语从句的时态用过去完成时不够合理。
C. Correct；the earliest date at which humans are known to have made stone tools.=humans are known to have made stone tools at that date (the earliest date) – AlienX.
D. 定语从句关系代词错误；are known to be doing sth.用法unidiomatic，要表示正在进行也只要are known to do即可。
E. date of + noun用法错误，其后面那个名词都是在某个时间出现的事件，如：date of birth、date of departure、date of marriage，而date of humans不是什么事件，所以不能说 date of；应该用are known to have made，因为known是发生在现在，make发生在known之前。
补充说明：
1. A中用关系代词when的正误：
From Ron(Manhattan)：
I'm pretty sure that either "when" or "at which" would be acceptable. (clearly, the latter is acceptable -- it appears in the correct answer, after all -- but i wouldn't object to the former.)
If you want to get really subtle, i think (not 100% sure) that "the date when" is used for actual, precise calendar dates, whereas "the date at which" is used for the usually more vague dates of historical events, such as the one in this problem. But i'm sure the test is not going to depend on this sort of nuanced difference.
2. 注意date to 后面是ago，而date at 后面是old。
date…..to可追溯sth到...几年，强调发生的时间点
P1-129
The teeth and jawbones found in Tanzania by Dr. Mary Leakey and dating to 3.75 million years ago are the oldest reliably dated human fossils.
G21-34
Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of adry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date at which humans are known to have made stone tools.
date….at年代判定、鉴别/ 年份有….年之久，强调发生到现在经过的时间有多长
G31-28
Rock samples taken from the remains of an asteroid about twice the size of the 6-nuke-wide asteroid that eradicated the dinosaurs have been dated at 3.47 billion years old and thus are evidence of the earliest known asteroid impact on Earth.
G13-28
Fossils of the arm of a sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on the Greater Antilles islands.
3. 另外date在OG 之可见用法如下：
date back: have its origin
date from: to reckon from some point in time
紫3
Native American burial sites dating back 5,000 years indicate that the residents of Maine at that time were part of a widespread culture of Algonquian-speaking people．
一个5000年前的北美遗址指出在那时期的缅因州居民是广大的Algonquian-speaking people文化的一部份
紫90
The concept of the grand jury dates from the twelfth century, when Henry II of England ordered panels of common citizens to prepare lists of suspected criminals in their communities.
Many of the earliest known images of Hindu deities in India date from the time of the Kushan empire and were fashioned either from the spotted sandstone of Mathura or from Gandharan grey schist.
另外附上prep中涉及到此知识点的两句：
Prep 1-232. (TTGWD4-Q1)
The Acoma and Hopi are probably the two oldest surviving Pueblo communities, both dating back at least a thousand years.
Prep 2-215 (GWD31-Q28)
Rock samples taken from the remains of an asteroid about twice the size of the 6-nuke-wide asteroid that eradicated the dinosaurs have been dated at 3.47 billion years old and thus are evidence of the earliest known asteroid impact on Earth.
257. (GWD6-Q30)
Though subject to the same wild-animal control efforts that killed off almost all the wolves in North America over the past century, the coyote's amazing ability of adapting to the presence of humans has enabled it to expand its range into Alaska and Central America.
A. coyote's amazing ability of adapting to the presence of humans has enabled it to expand its
B. coyote, because of its amazing ability of adapting to the presence of humans, have been able to expand their
C. coyote, because of its amazing ability to adapt to the presence of humans, has been able to expand its
D. amazing ability of the coyote to adapt to the presence of humans have enabled it to expand the
E. amazing ability of the coyote to adapt to the presence of humans has enabled it to expand the
题目释义：Though subject to…, the coyote, because of sth., has been able to expand its range into…
考点：
句子结构（grammatical construction） 逻辑意思（logical predication） 主谓一致（agreement）
1. 固定搭配：ability to do sth.有能力做某事；ability of sth./sb. 某某某的能力。
2. Be subject to sth：If someone or something is subject to something, especially something bad, it is possible or likely that they will be affected by it. 其中subject是形容词。
选项分析：
A. 逻辑主语错误，能subject to… 的应该是一个人或物，而不是一种能力；it和its逻辑上是指the coyote，但语法上却指代了the ability；ability of doing搭配错误。
B. have和their与主语和指代对象coyote为单数不一致；ability of adapting--unidiomatic。
C. correct。
D. subject to的逻辑主语错误；have用了复数主谓不一致；the range用了定冠词，可是前面并没有提到过该range，因此定冠词使用错误
E. 逻辑主语错误；the range错误同D
258. (GWD-9-Q2)
In an attempt to produce premium oysters, a firm in Scotland has developed a prototype of a submersible oyster farm, sitting below the surface of the ocean, and it provides ideal conditions for the mollusks' growth.
A. farm, sitting below the surface of the ocean, and it provides
B. farm, sitting below the surface of the ocean for providing
C. farm that sits below the surface of the ocean and providing
D. farm that sits below the surface of the ocean and provides
E. farm that is sitting below the surface of the ocean and it provides
题目释义：In an attempt to do sth., a firm has developed a prototype of a farm that sits…and provides…
考点：
逻辑意思（logical predication） 平行结构（parallelism）
1. in an attempt to需要考虑逻辑主语。
2. 定语从句谓语的平行，不需要补出that，相当于共享了句子成分，如在本句中共享了主语；不似宾语从句两个名词性从句的平行需要补出从句引导词，如that/whether等。
选项分析：
A. it provides与前面整个分句并列，所以it也就指代了a firm，逻辑意思错误，应该指代submersible oyster farm；sitting引导的短语做状语修饰前面的分句，而不再是做限定性定于修饰farm，逻辑错误。
B. sitting引导的短语错误同A；表动作的目的用不定时比用for doing好，所以用for providing不佳。
C. and前后不平行。
D. correct；sits和provides平行。
E. 定语从句可以前后共享主语，不需要再补出it；用了现在进行时表示了一种潜在含义：以后这个farm可能会移动，逻辑意思荒诞。
