无线频道间隔为25kHz的负控系统,其最大允许频偏为()。
A.±2kHz;
B.±3kHz;
C.±4kHz;
D.±5kHz。
参考答案:D
人感知声音的基本过程是这样的:外界传来的声音引起______振动,这种振动经过________及其他组织传给_______,__________再把信号传给大脑,这样人就听到声音了。
情景交际。
1. 当你和陌生人第一次见面时,应说:[ ]
A. How are you?
B. How do you do?
C. You are welcome.
2. 你想和李明通电话,应说:[ ]
A. Hello! Are you LiMing?
B. Hello! I'm Jack, who are you?
C. Hello! May I speak to Li Ming?
3. 你要问朋友是否喝茶时,应说:[ ]
A. What would you like?
B. Would you like some juice?
C. Would you like a cup of tea, please?
4. 买衣服询问价格时,应说:[ ]
A. How much are they?
B. How many clothes are there?
C. What do you want?
5. 当你向别人介绍你的朋友Jim时,你应说:[ ]
A. This is Jim.
B. He is Jim.
C. You are Jim.