We our foreign teacher since he to America.
- A.haven’t heard from; returned
- B.didn’t hear from; returned
- C.didn’t hear from; returns
- D.haven’t heard from; returns
答案
正确答案:A
知识点:现在完成时;一般过去时

自从我的外教回到美国,我们再也收到他的来信。根据关键词since he moved to Beijing可知,本句是现在完成时态,排除B和C。return to America发生在过去。所以答案选A。

略
