句型转换。

1. They swam in the river.（用at that time  yesterday改写句子）  

    They _______ _______ in the river at that time  yesterday.

2. The students were having a meeting when the  teacher came in.（用while改写句子）

    ________ the students________ __________ a  meeting, the teacher came in.

3. The building is very high.（改为感叹句）

    _________ _______ the building is!

4. I was sleeping when he called me.（对划线部分提问）

    ________ ______ you __________ when he called  you?

5. I don't know what I should do.（改为同义句）    

    I don't know what _________ _____.