简述从物质载体角度对公文的分类。

Some children want to challenge themselves by learning a language different from _____ their parents

speak at home. [ ]

A. what

B. that

C. which

D. one

补全对话。

A: Have you got a computer??

B: 1._____

A: 2._____

B: I can read and do my homework on it.?

A: How can you do your homework on it?

B: 3._____ and open a new document.?

A: Can you write in it?

B: 4._____

A: How do you give it to our teacher?

B: 5._____

A: That’s great.

A.I can print it.?

B. Yes，I have.?

C. What can you do on it?

D. Switch on the computer?

E. Yes.

股骨颈骨折愈合过程中，不出现外骨痂的原因是（）。

A.股骨颈骨折后血肿太多

B.股骨颈无骨外膜

C.股骨颈无骨内膜

D.股骨颈血液供应差

E.股骨颈骨折损伤严重，难以形成骨痂

什么是回转壳体、经线、纬线？经线和纬线各有何特点？常见回转壳体的母线分别是什么？

关于8AS－12.5型制冷压缩机，下列说法正确的是（）。

A.该压缩机为8缸

B.制冷剂为氟里昂

C.气缸排列形式为扇形

D.气缸直径为12.5cm