将下列句子按要求改写。

1. There is some water in the bottle. (改为否定句)

    There ________________water in the bottle.

2. This skirt is 49 yuan. (对划线部分提问)

    ________________ is the skirt?

3. We had our first class at 9:00 yesterday. ( 改为一般疑问句)

    _______ you ______ your first class at 9:00 yesterday?

4. My brother is reading a book under the tree. (对划线部分提问)

    ________ your brother ________ under the tree?

5. They are doing some shopping at the moment. (用an hour ago改写)

    They ___________________ an hour ago.

谈判的准备阶段应该尽量做好哪四项工作。