This is a street crossing （十字路口）.There are res and g____ lights at eachcorner （交叉路口）.Drivers must watch the light c____       When there is a green light ,the cars may go on .When there is red light ,the cars must s____.They must wait u_____ the red light changes to green .Then  they can go on .Sometimes the cars want to make a right t_____ or a left turn .They can make a r____ turn when the light is green or red .But they must wait until the green light is shining if they want to turn l____ .         Some people are color-blind .They cannot see the d____ between red and green .These people must not d____ ,or else there will be accidents （事故）.We must k____ our street safter.