21. In my experiments, the liquid is cooled to 32¬¬¬ºF. It always freezes. A. If you cool the liquid to 32 degrees, it froze. B. If you cooled the liquid to 32 degrees, it would freeze. C. If you cool the liquid to 32 degrees, it will freeze. D. If you had cooled the liquid to 32 degrees, it would have frozen. 22. It may rain this afternoon. I hope it doesn’t because I don’t want the match to be cancelled. A. If it rains, the match is cancelled. B. If it rains, the match will be cancelled. C. if it rained, the match would be cancelled. D. If it had rained, the match would have been cancelled. 23. Unfortunately, I don’t know Philosophy, so I can’t answer your question. A. If I know Philosophy, I can answer your question. B. If I know Philosophy, I will be able to answer your question. C. If I knew Philosophy, I would be able to answer your question. D. If I had known Philosophy, I would have been able to answer your question. 24. _____ there are some more ideas, we can end the meeting now. A. If B. As if C. Unless D. In case 25. If he _____ with us now, he _____ the beauty of nature of the National Park. A. is / can enjoy B. was / will enjoy C. has been / would enjoy D. were / could enjoy 26. If they had searched more carefully, they…the watch sooner. A. will find B. would find C. found D. would have found 27. If I had got up early, I _____ to have breakfast now. A. have B.I had C. would have D. would have had 28. I cannot buy a new computer _____ I save enough money. A. if B. even if C. unless D. as if 29. Most people you meet will be polite to you _____. A. if you are polite to them B. if you will be polite to them C. unless you are polite to them D. if you were polite to them 30. If you do so, it _____ the matter worse. A. makes only B. would only make C. will only make D. had only made 31. You _____ English fluently unless you practice it every day. A. will speak B. will not speak C. can speak D. did not speak 32. Hurry up _____ you will miss the bus and be late for school. A. if B. and C. or D. as 33. You will get a good seat if you _____ first. A. come B. came C. have come D. will come 34. Sam will not graduate_____. A. if he passed all the tests B. if he does not pass all the tests. C. unless he passes all the tests D. unless he had passed all the tests. 35. If I had time, I would go with you. A.I am free and surely go with you. B.I am too busy to go with you. C. I will go with you because I have time. D. I am free enough to go with you. 36. If Margaret hadn’t been wearing a seat belt, she…. Injured. A. has been B. would has been C. would be D. would have been 37. If I _____ the rain yesterday, I_____ ill. A. had not caught / would have been B. had not caught / would have not been C. have not caught / were not D. have not caught / would have been 38. He looked frightened as if he _____ a ghost. A. sees B. is seeing C. has seen D. had seen 39. What _____if there _____ a serious nuclear accident. A. will happen / was B. happens / were C. would happen / were D. would happen / had been giúp em với em cảm ơn ạ