按要求进行句式转换，每空一词。

1. We want to eat fish. (改为一般疑问句)

_________ you _________ to eat fish?

2. I have breakfast at school. (改为否定句)

I _________ _________ breakfast at school.

3. Would you like some tea? (进行否定回答)

_________, _________.

4. How much for one apple? (改为同义句)

How much _________ one apple?

5. It’s time for school. (改为同义句)

It’s time _________ _________ to school.

下列哪项是位于延髓腹外侧浅表部位的中枢化学感受器的生理刺激因子()

A．二氧化碳

B．氢离子

C．钠离子

D．氧分压下降

E．氮气