1."I don't think that's a good ____ for parking the wrong pl

1."I don't think that's a good ____ for parking the wrong place .You'll have to pay the fine(罚 金 ) ".said the policeman .
A.idea B.excuse C.reason D.thought
请问这一题到底是选A还是选B?我的资料上给的答案是A,但是在别处却又看见说答案是B的.请问到底该选哪个?
2.Have you seen such big ___?
A.a tomato B.tomato C.tomatoes D.tomatos
给的答案是C,请问为什么不能选A?
3.I really don't know if I can borrow the book in ___.
A.the library of the school B.the school's library
C.the library of schools D.the school library
这一题为什么要选D?为什么不能选A或者B?
第一问说错了,我书上给的答案是B,别处的答案才是A.不过也没有太大问题是吧.