选择合适的词补全短文。

A. clean  B. off  C. play  D. be  E. wait  F. rules  G. mustn't  H. old  I. should  J. obey

There are many  in our life. We should  the rules. We must  for the green light. We  cross the road when the light is ted. It's very dangerous. And we mustn't on the road. We mustn't pick the flowers in the park. And we must keep  the grass. We must  quiet in the library or in the hospital. If we meet  people, we should help them. We  take good care of young children. We mustn't litter and spit everywhere. We should keep our environment(环境)  and be polite to everybody.