往复活塞压缩机一次工作循环包括（）四个工作过程。A.气体膨胀、

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问题单项选择题

往复活塞压缩机一次工作循环包括（）四个工作过程。

A.气体膨胀、吸气、压缩、排气

B.吸气过程、封闭运输、压缩、排气

C.吸气、压缩、膨胀

D.封闭、压缩、排气

答案

参考答案：A

填空题

用适当的介词填空。

1. What's that _____ English?

2. Please call his uncle _____ 656

-4869.

3. We want four English teachers _____ our new school.

4. Thanks _____your letter.

5. Here is a photo _____ Nick's family.

6. Can you take these pens_____ his uncle?

7. Mary has lots _____ friends in Shanghai.

8. My grandfather usually has hamburgers_____ breakfast.

9. The price _____ the hat is two dollars.

10. We sell pants _____ only fifteen dollars.

填空题

川乌的双酯型生物碱的毒性为无酯型的（）至（）倍。