[求助]

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

这道题我开始选的是e，但答案是a，我想问e选项在语法上有错误吗？

因为前后主语不同

E的话，placed的逻辑主语是前面的single locusts ，而实际不是；前面是独处的 locusts ，我想你总不可能把所有独处的locusts 都抓起来和其他同类关在一起吧，所以指代对象不同