单句改错,每句有一处错误.1、I found the book she lost three days before.2

这些改错都是时态有关,
1、I found the book she lost three days before.(lost前加had,丢这个动作发生在found之前,所以过去完成时)
2、By the end of this year,the factory will produced 20000 tractors.(will后加have,到今年年底,这个工厂将会生产出20000拖拉机.将来完成时)
3、I studied English since I was ten.(studied前加have,since和完成时连用)
4、We have been waiting for her for two hours by the time she came.(have改had,她到来是个过去工作,等待应该是过去的过去,过去一直在等,所以过去完成进行时)
5、Is this the second time he breaks the world record in the field and truck events?(breaks改成has broken,第几次后应该加现在完成时)
6、We didn't see him at the lecture yesterday.He mustn't attend it.(mustn't改成couldn't或can't,对过去的推测应该用couldn't/can't have done,must表推测只能用在肯定句)
7、Xiao Li is so wet.She must fall into the lake.(fall前加have,must have done对过去的肯定推测)
8、He slipped into the room conen no one looked at him.（好像有错误啊,实在该不出来）

1 book 后加that
2 produced改为produce
3 since 改为when
4 waiting 改为waited
5 and 改为of
6 have attended
7 fall 改为have fallen
8 conen 后加and

1 had lost
2 will have produced
3 studied---have studied
4 have---had
5 breaks---broke
6 mustn't---couldn't
7 must---may
8里的conen不是单词，有可能是名字所以应该是后面加个介词and
相信我吧，呵呵，这是初中的题吗？
我大学的专业就是英语