题目内容：

单句改错(每句一处错误,或多一词,或缺一词,或错一词)
1.Shanghai is larger than any other city in Africa.
2.Parents were busy,so they couldn't help cleaning the floor.
3.It is sure that he will win the first place in the contest.
4.He won't possibly allow you smoking here,as he dislikes it.
5.He was last seen making up a story to add up to the book.
6.He has hidden in the high mountain since ten years ago.