几道英语语法题目!我都知道答案的就是不知道为什么这么做.麻烦解说详细点并且清楚点.1、It's very kind __

几道英语语法题目!
我都知道答案的就是不知道为什么这么做.麻烦解说详细点并且清楚点.
1、It's very kind ____ you.I know it's very hard ____ you to do that.
A.of...for B.for...of C.for...for D.of...of
【为什么选择A?】
2、I'm afraid we haven't any skirts _____ your size.
A.in B.of C.for D.with
【为什么选择B?不是有个词组是in one's size?】
3、Your house is _____ mine.
A.twice as big as B.as big as twice C.as twice big as D.as big twice as
【为什么选择A?】
4、The library must ____.
A.be kept quiet B.kept quiet C.keep quiet D.keep quietly
【为什么选择A?而不是C?】
5、Someone says there is no air or water on ____ Jupiter（木星）.
A.the B./ C.a D.an
【星球不是独一无二的吗?为什么不+the?而选择B?】
6、Some people prefer to _____ spectators.
A.do B.make C.be D.being
【为什么选择C?prefer to 不是一个词组吗?】
7、Mr.Carter ____ the DVD player for 200 dollars.
A.paid B.spent C.cost D.purchased
【为什么选择D?不是有个词组是pay 】
8、I'll spend ____ minutes on my homework.
A.a little B.a little more C.a few more D.much more
【为什么选择C?而不是选择D?】