Every day some people are killed（被杀）while they are crossing the roads. ______ of these people are old people and children. Old people are often killed because they can't see or ______ very well. Children are killed because they are not ______. They forget to look and listen before they ______ the roads. A car or a bus can’t stop ______. If a car is going very fast, it will travel many metres ______ it stops. Some people don't always understand this. They think a car can stop ______ a few metres. It is difficult to ______ how fast a car is moving. The only way to cross the roads safely is to look ______sides, right and left. Then if the roads are ______, you can cross them.