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 is long, the sscattering 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 places see the lights. It helps drivers slow down or stop in time. So there will be fewer accidents. Moreover, 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.
According to the passage, the scattering of the red light is the _______.

A．longest

B．weakest

C．farthest

D．brightest

The underlined word “wavelength” means________ in Chinese.

A．光波

B．波浪

C．波长

D．光波

What can the red light help drivers do?

A．It can make drivers stop in time.

B．It can help drivers act more slowly.

C．It can help drivers see the lights in farther areas .

D．A and C

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 lights

D．The colors of the traffic lights