空气压缩机转速不变时，降低出口压头对空气流量变化的影响是（）。

A、无影响

B、可增加出口空气流量

C、可降低出口空气流量

D、可导致出口空气流量在一定范围内波动

补全单词。

1. What's the m _____ with you, Tom?

2. I'm so t _____ because it's hot today and I walked for a long time.

3. Look! A boy is l _____  (lie) on the grass and looking at the sky.

4. I have to see the dentist because I have a t _____ .