问题
单项选择题
对于音速．如下说法正确的是：（）.
A、只要空气密度大，音速就大
B、只要空气压力大，音速就大
C、只要空气温度高．音速就大
D、只要空气密度小．音速就大
答案
参考答案：C
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对于音速．如下说法正确的是：（）.
A、只要空气密度大，音速就大
B、只要空气压力大，音速就大
C、只要空气温度高．音速就大
D、只要空气密度小．音速就大
参考答案：C
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| Nowadays we call see more and more electric bikes in the street. Electric bikes are easy to 1 and they can run faster than ordinary bikes. So they become very 2 in many cities in China now. But the electric bikes also 3 many traffic accidents happen. So the Chinese government plans to make a new 4 for the electric bike riders (骑车者). If 5 electric bike is heavier than 40 kilos and it can go 6 than 20 kilometers an hour, its rider must get a license (执照). It means riders have to pass driving test 7 they ride their electric bikes on the road. People have different ideas about the rule. Some people like the rule 8 they think it will make the street much safer. But some people are not 9 the new rule at all. One rider said, "I don't want to get a license or 10 , I don't like too many rules in life." What's your idea, my friends? | ||||
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