A.I've been or I was?
现在完成时可以表示一直持续到现在的状态 We've lived here for ten years
一般过去时表示过去的状态，即已经结束的一段时间里的状态 We lived for ten years
B.have you (ever)...? & Did you (ever)...?
现在完成时可以表示迄今为止的一段时间里的动作 This young director has made four films so far
一般过去时表示过去的动作，即已经结束的一段时间里的动作 The director made many films in his long career
ps.(奇葩练习题)（答案b）
Did you know old MrGreen?~No,I never met him.
a.Mr Green is probably alive b.Mr Green is probably dead
C.today,this week...
现在完成时用today和带有this的短语表示迄今为止的一段时间 It hasn't rained today
一般过去时用yesterday和带有last的短语用于表示过去的一段时间 It rained yesterday
*有时today可以表示过去的一段时间 I haven't seen Rachel today.
