+ Đổi hình thức khẳng định sang phủ định hoặc ngược lại
+ Bỏ các liên từ nối (_________________)
- “ Unless = If …not” ( nếu …không, trừ phi)
Ex1: If you don’t study hard, you’ll fail in the exam.
Ex2: If she doesn’t water these trees, they will die.
=> Mệnh đề sau “ unless” là mệnh đề ở thể khẳng định => do đó khi đổi một câu điều kiện với từ nối “IF” sang “ UNLESS” nhớ lưu ý trường hợp mệnh đề “IF” ở thể khẳng định không được đổi sang thể phủ dịnh khi dùng “ UNLESS” mà phải đổi mẹnh đề chính sang thể ngược lại. Ex1: If I have time, I’ll help you.=> Unless
Ex2: If we had more rain, our crops would grow faster. => Unless
EXERCISE III . Choose the best answer :
1.I would never have believed _______ it with my own eyes.
A.if I didn’t see B.if I hadn’t seen C.if I haven’t seen D.if I wouldn’t have seen
2.Don’t worry ________ home late tonight.
A.when I’ll B.If I’ll be C.unless I’ll be D.if I’m
3.If I ________ the flu, I would have joined you for the trip.
A.hadn’t had B.haven’t had C.didn’t have D.had had
4.Jeff wouldn’t have bumped into the waitress if he _______ in such a hurry.
A.weren’t B. hasn’t been C.hadn’t been D.wouldn’t have been
5.If you ________Mary by chance, please give her my phone number .
A.met B.meet C.could meet D.will meet
6.I think she would forgive you if you _______ to speak to her .
A.are trying B.would try C.tried D.have tried
7. I wouldn’t have to take this course if my English _______ better.
A.were Bhad been C.would be D.would have been
8.If we hadn’t got lost , we _______ arrived much earlier .
A.had B.would be C.might be D.could have
9.If I _______Japanese was so difficult , I wouldn’t have taken it up.
A.knew B.had known C.would have known D.might have known
10. If it ________ warm yesterday, we would have gone to the beach.
A. was B. were C. had been D. could be
11. _________ that problem with the car, we wouldn’t have missed the speech.
A. If we had had B. If had we had C. C.Unless we had had D. Provided that we had had
12. If I were a little taller, I _________ be able to water the plant on the top shelf.