想一想，选一选。

1. 当你问别人“全家福上都是谁”时，你应说：[ ]

A. Who are they?

B. Who is it?

2. 当你想告诉别人“我家有三个家庭成员”时，你应说：[ ]

A. My family has four members.

B. My family has three members.

3. 当你向别人介绍你叔叔的体貌特征时，你可以说：[ ]

A. My uncle is thin.

B. My uncle likes music.

离心式压缩机轴向推力的平衡方法有（）和（）。