1. If you don't study harder, you'll fail the next exam.

->Unless you study harder, you'll fail the next exam.

2. If he doesn't practice writing every day, he can't improve his writing skill.

->Unless he practices writing every day, he can't improve his writing skill.

3. Unless this man is a driver, he can't help you move by car.

-> If this man isn't a driver, he can't help you move by car.

4. Unless you go out more often, you might fall ill.

->If you don't go out more often, you might fall ill.

5. If you don't return this book to the library today, you'll have to pay a fine.

->Unless you return this book to the library today, you'll have to pay a fine.

6. Unless he cleaned up the car now, his boss could ask him to do this.

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

7. Unless they were absent now, they would meet the headmaster.

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

8. If I didn't know the number, I would not ring her up.

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

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Unless=If not (không, trừ khi)

*ĐK 1:

• If + S + do/ does+ not + V (nguyên thể)+ O, S + will ()+ V (nguyên thể)

=> Unless + S + V (chia theo S ở thời hiện tại)+ O, S + will+ V (nguyên thể)

• If + S + is/am/are+ not +…, S + will ()+ V (nguyên thể)

=> Unless + S + is/am/are + …, S + will+ V (nguyên thể)

*ĐK 2:

• If + S + did not+ V (chia ở thời quá khứ đơn)+ O, S + would+ V (nguyên thể)

=>Unless + S + V (chia ở thì quá khứ đơn)+ O, S + would+ V (nguyên thể)

• If + S + were/was + not + to + V (nguyên thể)+ O, S + would+ V (nguyên thể)

=> Unless + S + were/was + to V (dang nguyên thể)+ O, S + would+ V (nguyên thể)

1. Unless you study harder, you won't fail the exam.

2. Unless he practices writing every day, he can't improve his writing skill

3. If this man isn't a driver, he can help you move by car

4. If you don't go out more often, you might fall ill

5. Unless you return this book to the library today, you will have to pay a fine

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

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

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