1. I (not see)…………… him since last Christmas. 2. We (go)…………….. to Vung Tau several times. 3. He already (write)………………. to his parents. 4. Lien (not prepare)…………… her lessons yet. 5. They just (receive)…………..a package from their grandfather. 6. Miss Huong (teach)………….us English for 2 years. 7……….she (feed)……her dog yet? 8. We never (take)……… a bus to school before. 9. Next week, my uncle (come)………..back home for Christmas. 10. My teacher is explaining the lesson but I (not understand)………..what he is saying. 11. Lan (be)………….my next door neighbor when I lived in Hai Phong. 12. They usually (go)…………fishing at weekends. 13. I (see)………….a movie tonight. Would you like (come)…………? 14. I prefer (walk)………to (go)…………….by bike. 15. Don’t (make)………….noise. The baby (sleep)…….. 6. I don’t know where the Sao Mai movie (be)………. 17. Her mother (give)………… her a new novel yesterday. 18. Ba can’t play soccer tomorrow. He (do)……… his homework. 19. When I (be)…………..young. I usually (play)……..with a kite. 20. My mother is interested in (cook)……. and she (cook)……..very well. 21. The 22nd SEA Games (take)……… place in my country two years ago. 22. They stopped (talk)…………..when the teacher came in. 23. It (rain)………._heavily now. 24. I (live)…………with my parents until I went to HCM city. 25. I hope that he (win)…….. the race. 26. She (do)………. her homework recently. 27. They (not hand)………..in their essay yet. 28. It is not safe (leave)…………medicine around the house. 29. I want (come)………with my mother. 30. In my country. Children (have to)…………. wear uniform when they go to school. 31. …….you (meet)…….the new student yet? 32. I (lose)…………..my handbag yesterday. 33. Going shopping (be)…………very interesting. 34. She already (finish)…….her homework. 35. My sister (get)………..married next month. 36. Tomorrow (be)………..Sunday. What ……you (do)……….? 37. The concert this evening (start)…………at8 o’clock. 38. I (wait)…….for her since half past six. 39. Do you think the population of the world (rise)……….very fast? 40. In 2030, every one (study)………at home using computer. 41. He (fall)……..asleep while he was watching TV. 42. I enjoy (play)…………soccer after school. 43. Don’t worry! She (come)………..back in a few minutes. 44. Nam(talk)…………with her many times. 45. It (rain)……….when I (wake up)……… 46. I (see)………an accident while I (drive)...…to my office. 47. She (be)………happy since she had a computer. 48. They (build)…………that building for two years. 49. We often (go)…………skiing in winter. 50. At the moment, she (read)….. in the library. 51. It’s a lovely day. The sun (shine)….. and the birds (sing)………. 52. What ....... she usually (do)……….in the evening? Gíup mk vs các bn ơi !

Để trả lời câu hỏi trên, bạn cần điền vào chỗ trống của mỗi câu với dạng đúng của động từ được đưa ra trong ngoặc.

1. I have not seen him since last Christmas.
2. We have gone to Vung Tau several times.
3. He has already written to his parents.
4. Lien has not prepared her lessons yet.
5. They have just received a package from their grandfather.
6. Miss Huong has been teaching us English for 2 years.
7. Has she fed her dog yet?
8. We have never taken a bus to school before.
9. Next week, my uncle is coming back home for Christmas.
10. My teacher is explaining the lesson but I don't understand what he is saying.
11. Lan was my next door neighbor when I lived in Hai Phong.
12. They usually go fishing at weekends.
13. I am seeing a movie tonight. Would you like to come?
14. I prefer walking to going by bike.
15. Don't make noise. The baby is sleeping.
16. I don’t know where the Sao Mai movie is.
17. Her mother gave her a new novel yesterday.
18. Ba can't play soccer tomorrow. He will be doing his homework.
19. When I was young, I usually played with a kite.
20. My mother is interested in cooking and she cooks very well.
21. The 22nd SEA Games took place in my country two years ago.
22. They stopped talking when the teacher came in.
23. It is raining heavily now.
24. I lived with my parents until I went to HCM city.
25. I hope that he will win the race.
26. She has been doing her homework recently.
27. They have not handed in their essay yet.
28. It is not safe to leave medicine around the house.
29. I want to come with my mother.
30. In my country, children have to wear uniform when they go to school.
31. Have you met the new student yet?
32. I lost my handbag yesterday.
33. Going shopping is very interesting.
34. She has already finished her homework.
35. My sister is getting married next month.
36. Tomorrow is Sunday. What will you do?
37. The concert this evening starts at 8 o'clock.
38. I have been waiting for her since half past six.
39. Do you think the population of the world is rising very fast?
40. In 2030, everyone will be studying at home using a computer.
41. He fell asleep while he was watching TV.
42. I enjoy playing soccer after school.
43. Don't worry! She will come back in a few minutes.
44. Nam has talked with her many times.
45. It was raining when I woke up.
46. I saw an accident while I was driving to my office.
47. She has been happy since she had a computer.
48. They have been building that building for two years.
49. We often go skiing in winter.
50. At the moment, she is reading in the library.
51. It's a lovely day. The sun is shining and the birds are singing.
52. What does she usually do in the evening?

3. He has already written to his parents.

2. We have gone to Vung Tau several times.

1. I have not seen him since last Christmas.

Để giải câu hỏi trên, ta cần biết các phản ứng hóa học của từng thí nghiệm:

(a) NH4NO3 (rắn) → NH4NO3 (lỏng) + N2O + H2O

(b) NaCl + H2SO4 (đặc) → NaHSO4 + HCl

(c) Cl2 + 2NaHCO3 → 2NaCl + H2O + CO2 + Cl2

(d) CO2 + Ca(OH)2 → CaCO3 + H2O

(e) SO2 + 4KMnO4 + 2H2O → 4MnO2 + 4KHSO4 + H2SO4

(g) KHSO4 + NaHCO3 → KHCO3 + Na2SO4

(h) PbS + 2HCl → PbCl2 + H2S

(i) Na2SO3 + H2SO4 → Na2SO4 + H2O + SO2

Từ các phản ứng trên, ta thấy có 5 thí nghiệm sinh ra chất khí là (a), (c), (d), (e), và (i).

Vậy câu trả lời cho câu hỏi trên là D. 5.