The English physician Edward Jenner found that if experimental subjects were deliberately infected with cowpox, which caused only a mild illness, they are immune from smallpox.
-
Awhich caused only a mild illness, they are immune from
分析该选项
-
Bcausing only a mild illness, they become immune from
分析该选项
-
Cwhich causes only a mild illness, they are immune to
分析该选项
-
Dcausing only a mild illness, they became immune from
分析该选项
-
Ewhich caused only a mild illness, they would become immune to
分析该选项
显示答案
正确答案: E