单词拼写（每题1分，共8分）

1.It is healthier to keep a b_______ diet every day.

2. The little boy e________ his living by selling newspapers.

3. I’ll come tomorrow,  if the weather p___________

4. Finally, they were able to s_______ shelter from the rain.

5. The first s________ of the play was moving.

6. It’s r_______ to interrupt, so you had better wait.

7. To succeed, we must c___________ talent with hard work.

8. The flower is i________ beautiful, but it produces no fruit.

流体在管内流动时，由于一定速度的流动产生的压力称为（）。

A、动力

B、重力

C、阻力

D、动压