新疆且末玉:几个英语问题请教各位!!!急！急！！急！！！

几个问题，关于从句的、日常用语的。
1，It was known to all that Williams had broken his promise that he would give them a salary rise.
问题：开头那个It能不能用What替代？还有这句话什么意思？

2，If the south had won the war, ??? is now the United States might have been divided into several countries.
问题：???处为什么只能用what而不能用that？还有这句话什么意思？

3，Does it matter much that they will not attend the meeting tomorrow? 这句话什么意思？

4, --What are you trying to prove to the police ?
--Where I was last night.
怎么翻译？

5，I am strongly conviced they have done their best and that things will be improved.
怎么翻译？

6, Mary's parents were very pleased ??? she had passed the entrance examination for high school.
???为什么不填东西？为什么不能填that？

7，--I'd rather have some wine if you don't mind.
--Of course not. Any thing you want.
Any thing you want.什么意思？

8，--Shall I give you a ride as you live so far away?
--Thank you. It could't be better.
It could't be better.什么意思？