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

A:Have you two met?B:No,but I heard a lot about him I've heard a lot about you.为什么这句话是现在完成时,而No,but I heard a lot about him 却用一般过去时? I ___ of Hongkong a lot,but I've never been there beforeA.hear B.heard C.have heard应该选择哪个时态啊? I have heard a lot of good things about you( )II have heard a lot of good things about you( )I came back from abroad.答案是since ,为什么不用before? i have changed a lot I have changed a lot I’ve heard a lot about you I’ve frequently heard about you 高考英语I have heard a lot of good things about you ________ I came back from abroad.A.until B.since C.when D.before Have you i( )the new?-No,I have never ( )such a thing.A.heard of;heard B.heard;heard C.heaHave you（ )the new?-No,I have never ( )such a thing.A.heard of;heard B.heard;heard C.heard of;heard of D.heard;heard of the boy asked( )any noise from outside.A.whether had I heard B.whether I had heard C.whether have I heard D.whether I have heard I have a lot of homework-----(do) I have a lot to learn I still have a lot to learn. I have a lot of toys 疑问句 I have a lot of housework________ i have caught a lot of_____this year I have a lot of (headache) I have a lot of both 翻译：Diogenes ,I have heard a great deal about you .