根据括号内所给的中英文提示，用单词或短语的适当形式填空。

1. The boy often ________ ( fix)  up bikes to make money for school on weekends.

2. Mr. Smith spends an hour ________ ( run)  every morning.

3. We can't put off ________ ( make) a plan to save the homeless people.

4. Not only my parents but also I ________ ( be) hoping to see my uncle soon.

5. We need to ________(想出) some ideas for making model robots

风机在不稳定区工作时，所产生的压力和流量的脉动现象称为（）。

A、脉动

B、串轴

C、喘震

D、共振