句型转换。

1. I play with my friends on Sundays. (一般疑问句)

    ______ you ______ with your friends on Sundays?

2. It is Monday. (针对划线部分提问)

   ______ ______ is it?

3. want, what, do, to, you, do (连词成句) ? 

    ___________________________________________

4. They are listening to the radio. (否定句)

    They ______ to the radio

什么是市场机制？市场机制主要包括哪些具体机制？