题目内容：

根据短文内容及所给提示，补全文中单词或用所给单词的正确形式填空

Now more and more cars are on the street. Traffic is b1.. Every year, many 2.(accident) happen. When we are 3.(walk) on the street, we should be c4., especially when crossing the street.

If we see someone badly hurt in an accident, we should give him or her first  a5.and call an ambulance.