This is a street crossing. There are red and green lights at each corner. Drivers must watch the lights carefully.
When there is a green light, the cars may go. When there is a red light, the cars must stop. They must wait until the red light changes to green. Then they can go on. Sometimes the cars want to make a right turn or a left turn. They can make a right turn when the light is green or red. But they must wait until the green light is shining if they want to turn left.
Some people are color-blind(色盲). They can not tell the difference(不同) between the red and green lights. These people must not drive, or there will be accidents. We must keep our streets safe.
Drivers must watch _____ carefully at each corner.
A.green lights         B.red lights            C.both green lights and red lights
When there is a red light _____ .
A.the cars must stop                B.the cars may go on      C.the cars may make a left turn
Cars can make a right turn when _____ .
A.there is a red light              B.there is a green light     C.there is a red or green light
Color-blind people may have accidents because _____ .
A.they can’t see cars
B.they can’t see the lights
C.they can’t tell the difference between the red and green lights
According to (根据) the passage _____ must not drive.
A.young people     B. color-blind people             C.old men