大全 GWD都没有的题~~~不知道出处,求助then的用法~~~

According to entomologists, single locuts are quiet creatures, but  when locusts are placed with others of their spiecies, they become excited, change color, vibrate, and even hum.

C. locusts,when placed with others of their spicies,

E. placed with others of their species, then

OA A

A,C,E看着都不太顺,请教NN~~~~

其实不是没有出处,而是在XDF小蓝上的,但是帖子基本都是大全和GWD上的

而且,我看到好多XDF的题答案都被论坛否了~~~

我觉得小蓝前半部分有的题真的很难理解,不知道是我太弱,还是题目本身太难

还有2个月考试,太没把握了~~~

恩，如果是小蓝上的题目就没问题了。

According to entomologists, single locuts are quiet creatures, but  when locusts are placed with others of their spiecies, they become excited, change color, vibrate, and even hum.

C. locusts,when placed with others of their spicies,

E. placed with others of their species, then

C和E的表达都不对；locusts,when placed with others of their spicies,划线部分不需要的。和后面的they重复了，一句话里不能有两个位置一样的主语。

E then不可以单独引导 完整主谓的句子的。

弱问一句,then是什么词性???做什么成分?

经常看到有and 和then连用的情况,怎么解释???