船上通风管系的作用是（）①防止货物变质或自燃；②改善人员的生活与工作条件；③调节舱内

Read and choose. (根据对话内容和中文意思填空)    

Boy: Let's play a guessing game (猜谜游戏). 

Girl: 1.           (太好了). 

Boy: It's an animal. It's 2.            (大的).

Girl: Is it a 3.            (狮子)?

Boy: No, it isn't. It has a 4.             (长的) nose and a 5.            (短的)tail.

Girl: Is it an elephant?

Boy: Yes. It's so 6.            (有趣的).

What does the speaker mean a. He learned a lot of experience from observing the street life. b. He learned how to take precautions against the criminals. c. He learned to be smart by the life in New York. d. He was confident as he walked through Times Square to his office every day.

在常用的铸造合金中，灰铸铁、硅黄铜的流动性最好，（）的流动性最差。

枸橼酸与碳酸氢钠组成的崩解剂在片剂中的主要崩解原理是（）

A.毛细管作用

B.改善了颗粒的润滑性

C.酶解作用

D.膨胀作用

E.产气作用

风机在运行中，风机和电机轴承瓦的温度不得超过（）。

A、45和50℃

B、50和60℃

C、70和65℃