阅读短文，完成题目。

Every year many children and old people have accidents (事故)when they cross the road. Some of them even die in accidents(死于事故).Children have accidents because they are not very careful(细心). They sometimes play on the road and do not look out for cars. Many old people cannot see or hear very well. They should not cross the road alone(单独的). To cross the road safely(安全地),you should look for a zebra(斑马) crossing. You can cross the road, when you see the green man. When there is no zebra crossing, you must look left, then right, and then left again. You should walk quickly, but you should not run on the road.