OG12-75

xiaoguolulu

A proposal has made to trim the horns from rhinonceroses to discourage poachers; the question is"wether tourists will continue to visite game parks and see rhinoceroses after their horns are" trimed.

A.whether tourists will continue to visite game parks and see rhinoceroses after their horns are
B.wheher tourists will continue to visit game parks to see one once their horns are
C.whether tourists will continue to visit game parks to see rhinoceroses once the animals' horns have been

答案是C。我想知道为什么once the animals' horns have been这里一定要用have been 形式，为什么不能直接用are呢？

bababa11111

'have been trimmed" reflects that the trimming must occur before the tourists arrive

Lyssazhao

GMAT语法对句子的逻辑关系清晰否考察的很严格。
句子关心的是说，切掉角后，人们是否还会来看犀牛。所以一定会用时态把这个动作的逻辑关系区分开。

sophia000

OG的解释是必须完全修整以后的效果，所以强调完成

mongmong

前面的人太棒了~赞一个~