句型转换。

1. She has studied English for three years. (改为一般疑问句)

    ________ she________ English for three years?

2. To protect the environment is important. (同义句)

   It is important ________ ________ the environment.

3. I have been to Shanghai twice. (对画线部分提问)

   ________ ________ times have you been to Shanghai?

4. We watch TV once a week.( 就画线部分提问)

    ________ ________ do you watch TV?

5. We must put some books in the bag. (改为否定句)

    We ________ put ________ books in the bag.