`1.` If they weren't absent now, they would meet the headmaster.

`2.` If he didn't clean up the car now, his boss could ask him to do this.

`3.` Unless I knew the number, I wouldn't ring her up.

`4.` Unless Peter studied hard, he could not get good marks.

`5.` Unless my sister had a terrible headache, she wouldn't be absent from her class.

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`` Unless `=` If...not : nếu không...thì

`-` Câu ĐK `2` : diễn tả `1` sự việc hay điều kiện không thể xảy ra ở hiện tại hoặc tương lai.

`+` If + S + V2/ed(not), S + would/could... + Vinf

`+` Unless + S + V2/ed, S + would/could.. + Vinf

Công thức câu điều kiện loại 2

Không có thật, trái với hiện tại hoặc tương lai

If + S+ V2 (quá khứ),    S+would/could+ V bare

Unless (trừ phi) +S +V = If +S+Aux. V + not +V

⇒Aux.V : trợ động từ (can/could/ may/might/have/has/will/would/be (was,were) , do/did,    ...... )

1. If they weren't absent now, they would meet the headmaster.

2. If he didn't clean up the car now, his boss could ask him to do this.

3. Unless I knew the number, I would not ring her up.

4. Unless Peter studied hard, he could not get good marks.

5. Unless my sister had a terrible headache, she would be absent from her class.