1.The workers had finished building the library ( ).

1.The workers had finished building the library ( ).
A.in 2004 B.since then C.for a year D.by that time
2.——Mike,you are supposed ( )your homework now,but you are watching TV!
——I have already finish my homework,Mom.
A.to do B.to doing C.to be doing D.to be finishing
3.——Do you want to see the film?
——No,I ( )it three times,I'm really tired of it.
A.will see B.have seen C.had seen D.am seeing
4.I want to live in a room ( )is neither too big nor too small.
A. B.where C.that D.what
答案是DCBC,想知道是为什么?