. Put the verbs in brackets in the correct verb tens

1. Tom (call) __________________ his boss yesterday.

2. I (meet) __________Robert at the supermarket this morning.

3. We (fly) _____________ to Ha Noi several times, but last summer we (go)______ there by train. 

4. When (your father/ give up) __________________smoking?

5. __________your uncle (move) ________ to Da Lat in 2005?

6. I (be) __________________ to Sa Pa twice since 2000. 

7. We (spend) __________________ our summer vacation in Ha Long Bay last July.

8._______________you  (ever, watch) __________________ the film Titanic?

9. __________________the postman (deliver) __________________ the letter half an hour ago?

10. I (hear) __________________ the good news from Mary a few minutes ago.

11. I (have)___________________

14. The match (just start) __________________ . Our team is playing very well.

15. He (lose) __________________ his credit card. He can’t find it anywhere.

16. Prices (go) __________________ up. Everything is more expensive nowadays.

17. (you/buy) _______________________ the laptop yet?

18. Miss White (work) _______________________ in Ha Noi from 2011 and 2014.

19. I’m really hungry. I ______________ (not have) lunch yet.

20. We ______________ (not have) a maths class last week.

In the USA students (1)start their secondary education at the age of 11. First they (2)go to Middle School for three years. Then they go for High School for four years, from the age 14 to 18. Some students (3)stay school when they are 16 and (4)find jobs. But most students (5) leave at High School still they are 18. Then they (6)take exams and they get " High School Diploma ". There aren't any national exams.

All students at secondary school in the USA (7)studyEnglish, maths, science, and P.E, but students (8) choose other subjects, so they don't all study the same subjects.

About 90% of students in the USA go to (9)state schools. About 10% go to (10)  privateschools. Most of the private schools are religious schools.

31. We__________havent seen ________ (not see) her parents yet.

32. His sister ______ has worked____________(work) for this company since 1995.

33. _________________(pay)._________________money for your mother yet?

34. ____Have ___you ever___ (eat)___eatten_____Sushi?

35. She (not/come)       ________havent come_________      here for a long time.

36. I (work)___________have worked______here for three years.

37. ______Have___________you ever ______been___________.(be) in New York?

38. You (not/do) …_________havent done________your project yet, I suppose.

39. I (just/ see)    _have just seen________________    Andrew and he says he _____has already done____________       (already /do)about half of the plan.

40. I      ________have just decided_________     (just /decide) to start working next week.

41. He_________________   (be)at his computer for seven hours.

42. She _________________   (not/have) any fun for a long time.

43. My father _________________   (not/ play)any sport since last year.

44. I’d better have a shower. I   _________________    (not/have) one since Thursday.

45. I don’t live with my family now and we    ________________       (not/see) each other for five years.

46. I      _________________      (just /realize)that there are only four weeks to the end of term.

47. (She/ eat) _________________   at the Royal Hotel yet?

48. This is the second time (he /lose)     _________________     his job.

49. Laura never (win)……………………………………. a beauty contest before.

50. I (listen) …………………………to the new Tom Waits CD yet.

thực hiện dao động của nguồn âm càng lớn

u mình thiếu

Tần số là số lần của một hiện tượng lặp lại trên một đơn vị thời gian. Hertz hay héc, ký hiệu Hz, là một đơn vị đo tần số Hertz hay héc, ký hiệu Hz, là một đơn vị đo tần số