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 _________ _____.