một hợp chất có phân tử gồm 1 nguyên tử của nguyên tố liên kết với 2 nguyên tử O và nặng hơn phân tử H là 32 lần

a) Tính phân tử khối của hợp chất

b) Tính nguyên tử khối của X cho biết tên và kí hiệu hóa học

Giúp mik vs ạ

1. I _______________ (meet) Arthur three weeks ago.

2. My friend ________________ (thank) me for what I had done for him.

3. People ___________________ (speak) English in most of Canada.

4. She ________ (play) the piano when our guests _______ (arrive) last night.

5. My mother __________________ (come) to stay with us next weekend.

6. Violets ______________________ (bloom) in spring.

7. My father ________________________ (not smoke) for 5 years.

8. He _____ (leave) home two weeks ago and we _____ (not hear) from him since then.

9. By next month, I _________________ (finish) my first novel.

10. Be quiet! The teacher ___________________ (be) angry.

11. By the end of last March, I ______________________ (study) English for 5years.

12. He __________________ (do) his homework before he went to the cinema.

13. By noon, I _________________ (wait) for her for two hours.

14. Up to now, the teacher _____________________ (give) our class five tests.

15. I’m preparing to support anything he ________________ (say) tomorrow.

I: Choose the best answer among A, B, C, or D.

1. When I last saw him, he _____ in London.

A. has lived B. is living C. was living D. has been living

2. We _______ Dorothy since last Saturday.

A. don’t see B. haven’t seen C. didn’t see D. hadn’t seen

3. The train ______ half an hour ago.

A. has been leaving B. left C. has left D. had left

4. Christopher Columbus _______ American more than 500 years ago.

A. discovered B. has discovered C. had discovered D. had been discovering

5. He fell down when he ______ towards the church.

A. run B. runs C. was running D. had run

6. We _______ there when our father died.

A. still lived B. lived still C. was still lived D. was still living

7. They ______ table tennis when their father comes back home.

A. will play B. will be playing C. play D. would play

8. John ______ a book when I saw him.

A. is reading B. read C. was reading D. reading

9. He always ________ for a walk in the evening.

A. go B. is going C. goes D. going

10. Her brother ______ in Canada at present.

A. working B. works C. is working D. work

11. Jack ______ the door.

A. has just painted B. paint C. will have painted D. painting

12. My sister ________ for you since yesterday.

A. is looking B. was looking C. has been looking D. looked

13. I ______ Texas State University now.

A. am attending B. attend C. was attending D. attended

14. He has been selling motorbikes ________.

A. ten years ago B. since ten years C. for ten years ago D. for ten years

15. By Christmas, I _______ for Mr. Smith for six years.

A. will have been working B. will work C. have been working D. will be working

16. I _______ in the room right now.

A. am being B. was being C. have been being D. am

17. I ______ to New York three times this year.

A. have been B. was C. were D. had been

18. I’ll come and see you before I _______ for the States.

A. leave B. will leave C. have left D. shall leave

19. The little girl asked what _______ to her friend.

A. has happened B. happened C. had happened D. would have been happened

20. He said he _______ return later.

A. will B. would C. can D. would be

21. Jack ________ the door.

A. has just opened B. open C. have opened D. opening

22. I have been waiting for you ______ .

A. since early morning B. since 9 a.m C. for two hours D. All are correct

23. Almost everyone _______ for home by the time we arrived.

A. leave B. left C. leaves D. had left

24. By the age of 25, he ______ two famous novels.

A. wrote B. writes C. has written D. had written

25. When her husband was in the army, Mary ______ to him twice a week.

A. was reading B. wrote C. was written D. had written

26. I couldn’t cut the grass because the lawn mower ______ a few days previously.

A. broke down B. has been broken C. had broken down D. breaks down

27. I have never played badminton before. This is the first time I _____ to play.

A. try B. tried C. have tried D. am trying

28. Since _______, I have heard nothing from him.

A. he had left B. he left C. he has left D. he was left

29. After I _______ lunch, I looked for my bag.

A. had B. had had C. have has D. have had

30. By the end of next year, George _______ English for two years.

A. will have learned B. will learn C. has learned D. would learn

31. The man got out of the car, ________ round to the back and opened the book.

A. walking B. walked C. walks D. walk

32. Henry _______ into the restaurant when the writer was having dinner.

A. was going B. went C. has gone D. did go

33. He will take the dog out for a walk as soon as he ______ dinner.

A. finish B. finishes C. will finish D. finishing

34. I will be glad if he _______ with us.

A. had gone B. did go C. went D. goes

35 Ask her to come and see me when she _______ her work.

A. finish B. has finished C. finished D. finishing

36. Turn off the gas. Don’t you see that the kettle ________ ?

A. boil B. boils C. is boiling D. boiled

37. Tom and Mary ______ for Vietnam tomorrow.

A. leave B. are leaving C. leaving D. are left

38. I ______ to the same barber since last year.

A. am going B. have been going C. go D. had gone

39. Her father ______ when she was a small girl.

A. dies B. died C. has died D. had died

40. Last week, my professor promised that he ________ today.

A. would come B. will come C. comes D. coming

Hai số có hiệu là 155. Biết thương của hai số là 4 dư 5. Tìm hai số đó

Choose the underlined word or phrase that needs correcting.

1. Christopher went to the market this afternoon. ->

2. The director arrived a hour ago. ->

3. It’s rain heavily now, and Peter left umbrella behind this morning. ->

4. It’s an long time since your friends last visited us. ->

5. You didn’t called me last weekend. ->

6. The company buy some land last week but then sold it. ->

7. She worked hardly for her exam last month. ->

8. She always drives her car careful so that she never has an accident. ->

9. Simon is enough tall to join in the basket ball club. ->

10. They are playing badminton every afternoon. ->

Làm giúp mik vs các bạn ơi💖💖💖