题目内容：

 

1.He taught in this school last year.(把last year改为 since last year)

   He _________ _________ in this school _________ last year.

2.They didn’t clean the classroom yesterday.（改为被动语态）

   The classroom _________ _________ yesterday.

3.We have already returned the books.（改为否定句）

  We _________ __________ the books ___________.

4.Rice is grown in China.（划线部分提问）

 _________ is rice ___________?