理解能力不佳的我希望哪位i可以详细的解释下,

理解能力不佳的我希望哪位i可以详细的解释下,
1.All the people staying in the building rushed out （D）they heard the fire alarm
A.hurriedly B.at once C.as quickly as D.immediately
immediately,为什麽C不能选?
2.I would have come to see you earlier,but i （C）too busy
A.had been B.were C.was D.would be
为什麽D不选?
3.When does the ceremony （B）?
A.happen B.take place C.take part in D.turn up
C,D排除,A,B的区别在哪里啊?
4.Keeping dogs should not be banned,but （A）to certain areas
A.limited B.limiting C.to limit D.to be limited
这道完全搞不清楚啊,详情的解析可以嘛
5.Two thirds of the building in the area（B）
A.needs repairing B.need repairing C.need to repair D.needs to repair
这题同上,
6.-Are you satisfied with this hotel?
-Not a little.We can't have a nicer one.
这段对话怎么翻译啊
7.have done sb.doing有这种用法吗,用在什么情况下