英语..时态语态..

英语..时态语态..
1.I （C）there little more than a week when I set to work with the scientist.
A.would be B.have been C.had been D.will be
为什么啊..
2.--Did you tidy your room?
--No,I was going to tidy my room but I(A)visitors.
A.had B.have C .have had D.will have
为什么不选B啊...
3.--It was really very kind of you to give me a lift home.
--Oh,don't mention it .I(A)past your house anyway
A.was coming B.will come C.had come D.have come
4.They (B)two free tickets to Canada ,otherwise they'd never have been able to afford to go.
A.had got B.got C.have got D.get
麻烦每个选项都说下为什么..