People who cannot tell all colors apart are said to be color-blind. Most color-blind people can see yellows and blues, but confuse reds with green. It is very rare for a person to be blind to all colors, but they may see everything in shades of black, white and gray.

It is interesting to point out that many color-blind people don’t even realize that they are color-blind, they don’t know that the colors they are seeing and naming are not the actual colors that people with normal vision can see. This can be dangerous when a color-blind person confuses the red and green of a traffic light.

Color blindness is thought to be inherited（遗传）and although doctors have tested color blindness, there is no cure to treatment for it.

小题1:There are four cards here, and each has two colors. Which card’s colors do you think a color-blind person can tell correctly?

A．Red, Green

B．Green, Yellow

C．Red, Brown

D．Brown, Yellow小题2:A color-blind person______.

A．always knows how color-blind he is

B．often gives the wrong name of colors

C．see everything as the same color

D．can hardly see something of strong colors小题3:It’s especially dangerous for a color-blind person to cross a street when_____

A．it is crowded

B．it is a dark night

C．there are no traffic lights at the cross of the streets

D．the traffic light turns red小题4:A person who is color-blind is believed to have something to do with_____.

A．his old age

B．his poor eyesight

C．his parents or grandparents

D．his living condition小题5:Up to now, doctors______.

A．have found a way to prevent a person from getting color-blind

B．have found a way to free a person from his color blindness

C．have been able to tell whether a person is color-blind or not

D．have made it quite clear the cause of color blindness