非增压舱航空器的机上人员昼间必须使用氧气的高度是（）A、3600米 B、4000米

根据下面对话内容及所给的首字母提示,在对话后的横线上写出对话中所缺的单词(单词必须写完整)

Zhou Lan(Z) and Bruce(B) are talking about learning English.

B: What do you find hardest in learnin

Z: I find listening really hard.Sometimes it's difficult to u_____:It's not easy to

catch its meaning.

B: Well,you need l_____of practice.The more you listen,the 3_____it becomes.

Z: But I don't find the best w_____to do that.Would you please lend me a

h_____?

B: W_____not get a radio?It's helpful to listen to English p_____on the radio.

Z: It s_____like a good idea.

B: Practise m_____,and you'll find l_____is not so hard.

Z: I'll try my best to do that.Thank you.

当节气门位置传感器产生断路或短路故障时，安全保险功能将节气门开度固定为（），控制发动机工作。

A、0°或25°

B、10°或20°

C、5°或30°

某电灯的电阻r＝50Ω，两端电压U＝10V，如该电灯工作100s，则它消耗的电能W＝（）

精加工时，高速钢车刀切削部分的几何角度后角取值为（）

A.4°～6°

B.6°～10°

C.8°～12°

D.10°～14°