在内燃机的“吸气”、“压缩”、“做功”、“排气”四个冲程中，将内能转化为机械能的是____冲程；常用水来给内燃机降温，是因为水的____ 比较大．

Clerk: ____ I help you?

Mary: Yes, please. I want a sweater.

Clerk: What ____ do you want?

Mary: Blue.

Clerk: Here you are.

Mary: How ____ is it?

Clerk: Nine dollars.

Mary: I'll ____ it. Thanks.

Clerk: You're ____.

实验室用氯酸钾和少量高锰酸钾混合加热能迅速制得氧气其主要原因是（　　）

地球上极昼、极夜现象出现的范围是（      ）