问题描述：
每个要写三句，第一句肯定，然后写否定和疑问句，包括回答
最佳答案：
can造句：
1.Jogging can be harmful to the health.
2.The story can’t be true.
3.Can I go now?
? Yes, you can./No, you can't.
may造句：
1.She may be still waiting for us.
2.He may not come today.
3.May I go home now?
? Yes, you may./No, you can't/mustn't.
must造句：
1.He must be at home.
2.You mustn't smoke here.
3.Must I clean the classroom now?
? Yes, you must./No, you needn't.
??