Mr Wang is my good friend.We _____-each other since 2005.A.knew B.have known C.had known为什么是have known 而不是had known 都是完成时啊.
问题描述：
Mr Wang is my good friend.We _____-each other since 2005.A.knew B.have known C.had known
为什么是have known 而不是had known 都是完成时啊.
答
have known是现在完成时，表示动作持续到现在
had known 是过去完成时，表示过去完成了某事
再看since这个标志，since引导的从句都用现在完成时
答
从现在的角度看，我们已经认识这么长时间了，只是表示完成时。而had done则表示过去的过去。
答
had known 是过去完成时,前面必须要有过去式出现,而前面句子是现在时,只能用现在完成时have known.