GWN-TN-19 各位大神解释下啊

ssysyjzmf

21. GWD28-Q21:
According to entomologists, single locusts are quiet creatures, but when locusts are placed with others of their species, they become excited, change color, vibrate, and even hum.

A.    when locusts are placed with others of their species,
B.    when placing them with others of their species, then
C.    locusts, when placed with others of their species,
D.    placing them with others of their species,
E.    placed with others of their species, then

这道题我选了C，答案是A，想不通啊

gui59106375

C是错误的，but locusts,如果做插入语，两个主句single locusts are quiet creatures和they become excited之间应该有个and，如果不是，就应该去掉locusts这个词，而且这道题的意思是：根据昆虫学的（研究），单个蝗虫是很安静的物种，但是当将其与别的亚种放置在一起时，就会很聒噪。。。。。明显是用but表示对比，B有then错了，d是悬垂修饰，不知道是向前修饰还是向后修饰，而且无论向前 还是想都，都是错的，E有then错，只有B是对的