Modal 情绪 和 态度 ，+ 动词原形
must 必须 mustn’t 禁止
- We must finish the homework within a week.
- Air pollution must be taken seriously.
- The government can solve the problem of water pollution.
- Tom could walk when he was only one year old.
- Will you marry me?
- I will travel abroad with my family.
- To some extent, expressions may influence emotions.
- Such bodily reaction might help moderate the work stress.
- Students should work hard to pass the exams.
- Those sick people should seek help from doctors.
- The details may be unknowable.
- Such searches must take years.