情态动词:Should, Must, Mustn't, Have To

"Should"用于给建议。"Must"和"have to"表示义务("have to"通常用于外部规定)。"Mustn't"意味着被禁止——这与"don't have to"(意味着不必要)非常不同。

Examples

• You should see a doctor.
• You must wear a seatbelt.
• You mustn't smoke here.
• I have to work on Saturday.
• You don't have to come if you're busy.

Common Mistakes

Practice

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