句型转换。

1. You must finish your homework today. (改成同义句)

    You ______ _______ finish your homework today.

2. Don't swim in the river! It's dangerous. (改为同义句)

    _______ _______ in the river ! It's dangerous.

3. She can play the piano, too. (改为否定句)

    She play the piano, _______.

4. What do you think of soap operas?(改为同义句)

     _______ do you _______ soap operas?

5. He went to watch a soccer match yesterday. (改成否定句)

    He _______  _______ to watch a soccer match yesterday.

根据《合同法》的规定，下列情形中，要约没有发生法律效力的是( )。

A．撤回要约的通知与要约同时到达受要约人

B．撤销要约的通知在受要约人发出承诺通知之前到达

C．同意要约的通知到达要约人

D．受要约人对要约的内容作出实质性变更