GMAT Sentence Correction (SC) | Re: According to entomologists, single locusts are quiet

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