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问题 选择题

善于归纳总结，是学习的好习惯。关于声现象中，以下知识结构错误的是[ ]

答案

答案：C

A、声波产生的条件是要有声源的振动，传播振动的介质，故A是正确，不符合题意；
B、声音种类分为两种：乐音和噪声，故B是正确，不符合题意；
C、声音的特性有三个：音调、响度和音色，故C是错误，符合题意；
D、减弱噪声的途径有三个，在声源处减弱、在传播过程中减弱、在人耳处减弱，故D是正确，不符合题意；
故选：C．
单项选择题

根据凸轮控制器的触头在电路中的作用，可分为（）种触头。

A.一

B.二

C.三
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单项选择题

This is a famous street in China. What is it It’s West Street. Why is it so famous Now let me tell you something (41) it.
West Street is in Yangshuo, Guangxi. It’s over 1,400 years (42) .It’s about 1,000 meters (43) . But it’s very clean and beautiful. In the street, there are (44) shops. The things in the shops are nice and cheap. Every day, lots of visitors come here. Many of (45) are foreigners. It’s a good place to practice speaking English. So West Street is called the biggest English corner. Some people (46) call it the earth village. Almost everyone in the street (47) English.
But you mustn’t ride your bike or drive your car in the West Street. You can only (48) here. Why Because it’s a walking street. In the street, you needn’t worry that you’ll be hit by cars. (49) happy!
West Street is a wonderful place to visit. (50) West Street.

[A] also [B] too [C] either
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