:2019年中考英语一轮题型组合练（外研版20套含答案）

2019中考英语一轮练（1）（阅读理解+完形填空+任务型阅读达）

(限时:20分钟)

一、阅读理解

A 

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交通安全 说明文 176 ★★★ 5分钟

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(媒介), if the wavelength is long, the scattering will be short. If the wavelength is short, 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 travels far. In fact, it travels faster on rainy days. 

Using the red light can