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
我的答案选D，正确答案是A
因为我觉得D比较简洁 且可以表示句子的意思