GWD-19 一道逻辑题，求分析！NN们！

lindaaniu

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    placing的逻辑主语是they（locusts），错
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

洛洛洛洛

这不是语法吗....