题目内容：

He hasn't heard from his friend________last month. A.since B.by the end of C.for D.until
since 和until有时好难选呀!就像上面这道题.怎样做啊?

优质解答

这道题应该选A since
因为题目中用了现在完成时,而since一般是现在完成时的标志
如果题目是这样：
He didn't hear from his friend________last month.
那么这道题就应该选until