the twin sisters have learned a lot ____they came to China A when B as soon as C since D after

问题描述:

the twin sisters have learned a lot ____they came to China A when B as soon as C since D after

选C。这算是现在完成时态的其中一种常见结构 :现在完成时+since+过去时,表示“自从过去的某个时刻开始,就......”,如:I've worked here since two years ago.

D

C

c.since用完成时