看图回答问题。

  What do you usually do on weekends?

1. I often___________.                      2.My brother usually ___________.

3.My father often ___________.         4. My friend sometimes___________.

5. Lucy usually___________.              6.Some students often ___________.

7.Girls always ___________.               8. Most boys often ___________.

9. My grandpa never ___________.    10. Katrina usually___________.

液体粘度越小，需要离心泵的轴功率（），而与叶轮摩擦产生温度越低。

A、越大

B、越小

C、不变

D、不能确定