Modals of Certainty and Deduction
1Công thức
must/can't/couldn't + base verb (present); must/can't/couldn't + have + past participle (past)2Giải thích
Must dùng khi gần như chắc chắn điều gì đúng; can't/couldn't dùng khi gần như chắc chắn điều gì không đúng. Thêm have + V3 cho quá khứ. Không dùng mustn't để suy đoán (dùng can't).
Must expresses near certainty that something is true, while can't or couldn't expresses near certainty that it is not true. Add have + past participle to talk about the past.
Dấu hiệu: obviouslyclearly
3Khi nào dùng
- Logical deduction about the present
- Logical deduction about the past
4Quy tắc cần nhớ
- The negative of must for deduction is can't or couldn't, never mustn't
- These forms are based on evidence, not on possibility
- Use perfect infinitive for past deductions
5Ví dụ
That must be Tom at the door; he said he'd come.
They can't be at work; the office is closed.
She must have left early because her desk is empty.
6Lỗi thường gặp
- He mustn't be at home; his car isn't there. (can't be at home)
- She must be arrived by now. (must have arrived)