题目选项分析

The gyrfalcon, an Arctic bird of prey, has survived a close brush with extinction; its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970's.

The gyrfalcon, an Arctic bird of prey, has survived a close brush with extinction, their numbers now fivefold what they were when the use of DDT was sharply restricted in the early 1970's.