1. The environment in our city school be improved.

2. More laws must be madeto prevent any possible dangers.

3. Teenagers should not be allowedto have part-time jobs.

4. Animals should not be trainedto serve human beings.

5. When must this work be done？

这些句子都包含了情态动词和被动语态的结构，强调了行为的承受者并表达了说话人的态度或意愿。