I. Sử dụng câu điều kiện loại I và loại II để viết lại câu
1. They don’t understand the problem.
2.They won’t find a solution 
3. Go right now or you’ll be late for the train.
4. Because you speak English unnaturally, they do not understand you.
5. We didn’t know your phone number, so we could not contact you.
6.Because Simon doesn’t live near his mother, he can’t visit her often.
7. She didn’t hurry, so she missed the train. 
8.John is fat because he eats so many chips. 
9.Bill never does anything if you don’t tell him what to do. 
=>Unless………
10. They don’t have enough time so they cannot do me a favour.
11. I must leave now, or I’ll miss the flight.
12.Hurry up, or we will be late for the exam.
13.Peter gets bad marks because he doesn’t prepare his lessons well 
14.He doesn’t apply for the job because he doesn’t have enough qualifications.
15. We can’t buy this car because it is very expensive.
II. Rewrite the second sentence in such a way that it has the same meaning as the one before it:
1. You can’t visit the United States unless you get a visa If you don’t get a visa, you can’t visit the United States
2. We don’t go on holiday because we have enough money If we didn’t have enough money, we would go on holiday
3. What a pity you fail your driving test! I wish
4. I’m sorry I miss your birthday party I wish
5. Unless someone has a key, we can’t get into the house We can
6. He’s sorry now that he doesn’t invite Molly to his party He wishes
7. Unless he phones immediately, he won’t get any information If he
8. Mr. Will lost his job because he was late every day If Mr. Will
9. My husband doesn’t leave the car keys, so I can’t pick him up at the station If
10. He doesn’t hurry, so he misses the train If
11. We don’t go because it rains If
12. I’m sorry that I’m not finishing my homework now. I wish
13. The child will die if nobody sends for a doctor Unless
14. Susan feels sick because she eats 4 cream cakes If
15. Maria doesn’t apply for the job in the library and regrets it now Maria wishes
16. John is fat because he eats so many chips If John
17. It’s a pity I don’t take my doctor’s advice I wish
18. The accident happens because the train driver ignore a warning light If
19. We get lost because we don’t have a map If
20. Mrs. Taylor doesn’t like living in such a small house Mrs. Taylor wishes
21. If Joe doesn’t change his ways, he will end up in prison Unless
22. If he doesn’t work harder, he’ll lose his job Unless
23. Elizabeth get a bad cold because she starts smoking cigarettes If Elizabeth
24. Joan will stay on at school unless she finds a good job before September If Joan