题目内容：

I have heard a lot of good things about you( )I
I have heard a lot of good things about you( )I came back from abroad.
答案是since ,为什么不用before?

优质解答

since是从我从国外回来起,直到现在,所以用现在完成时,如果用before,时态应改为过去完成时,即had heard