问题补充：
When the traffic lights turn red, we will stop driving a car or crossing a street. Why is red used for traffic lights instead of other colors?
As we know, scattering(散射) happens when light goes through the air. For the same media(媒质), if the wavelength islong, the scattering will be short. If the wavelength is short, then the scattering will be long.
Of all lights we can see red has the longest wavelength, so the scattering is the weakest. That means the red light travels far. In fact, it travels farther on rainy days.
Using the red light can help drivers in farther areas sec the lights. It helps drivers stow down or stop in lime. If drivers don see the red light until they are close, they may not be able to stop the car in time. An accident may happen Red can also excite people. We can act more quickly when we see the color red. In a word, red lights help drivers stop in time and help prevent accidents.
【小题1】 When the traffic lights turn , we will stop driving a car.
A. red B green C. yellow
【小题2】According to the passage, the scattering of the red light is the .
A. longest b. weakest C. farthest
【小题3】 The underlined word wavelength means in Chinese.
A.波浪 B.光波 C.波长
【小题4】 What can the red light help drivers do?
A. It can help drivers in farther areas see the lights.
b. It can help drivers slow down or stop in time.
C.A and b
【小题5】Which of the following is the best title?
A. Why do accidents happen
b. How does the red light travel
C. Why do we use red traffic lightsA
答案：
(答案→)A
解析：
【主旨大意】本文讲述了为什么交通灯中，使用红色作为停车的标志。
【小题1】细节理解题根据第一段的第一句：When the traffic lights turn red. we will stop driving a car or crossing a street.可知。
【小题1】细节理解题根据第三段的第一句：Of all lights we can see red has the longest wavelength, so the scattering is the weakest.
可知。
【小题1】 词义理解题句意为：如果波长长，那么散射短。
【小题1】细节理解题根据最后一段的第一句 ：Using the red light can help drivers in farther areas see the lights, it helps drivers stow down or stop in time. 可知。
【小题1】主旨大意题 由本文的第一段提出问题：Why is red used for traffic lights instead of other colors? 可知。
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