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 _________ _____.