Mg có 3 đồng vị có số khối là 24,25,26.Cứ 5000 nguyên tử Mg có 3930 đồng vị 24,505 đồng vị 25 còn lại là đồng vị 26.Nguyên tử khối trung bình của Mg là

Trong tự nhiên lưu huỳnh có 3 đồng vị trong đó % số nguyên tử lần lượt là  ³²S(95%),³³S(0,8%),³⁴S(4,2%).Số nguyên tử các đồng vị ³²S và ³⁴S khi có 4 nguyên tử đồng vị ³³S lần lượt là

. Những điều khẳng định nào sau đây không phải bao giờ cũng đúng? A. Số hiệu nguyên tử bằng điện tích hạt nhân.   B. Trong nguyên tử số proton bằng số nơtron. C. Số proton trong hạt nhân bằng số e ở lớp vỏ nguyên tử.         D. Chỉ có hạt nhân nguyên tử Na mới có 11 proton

12. He used to fall asleep without (take) ___________________________ his shoes off.

13. My watch keeps (stop) ___________________________.

14. I remember (meet) __________________________ you somewhere last month.

15. The boys next door used (like) ___________________(make) ______________________ and (fly) __________________ model aero planes, but they seem to have stopped (do) __________________ that now.

8. I didn't like (cross) ............. it because of the bull. I never see a bull without (think) _________________that it wants (chase) _______________________ me.

11. The people in the flat below seem (be) to be  having a party. You can hear the champagne corks (thud)_____________________ against their ceiling.

12. He used to fall asleep without (take) ___________________________ his shoes off.

11. I am afraid you can’t borrow his car right now. It ..................... in the garage.

A.is repaired                           B.repairs                               C. repairing                           D. is being repaired

12. Up to the present, fourteen books ................. by Jane, a friend of mine

A.has been written                 B.are written                        C. were written                    D. will be written

13. The washing - up ..................... carefully.

A.should do                           B.should done                      C. should be done                D. should be do

14. The acupoints ................. to enhance the healing capability of the body itself.

A.stimulate                             B. stimulating                       C. stimulated                        D. are stimulated

15. Choose the word whose underlined part is pronounced differently from the others.

A.crazy                                   B.cream                                C. crown                               D. decide

16. Lately, several oils, including rose and lemon, ....................... to relieve anxiety, stress and depression

A.show                                   B. have shown                     C. have show                        D. have been shown

17. Choose the answer which needs correcting: People say that this house has been built by an old man 12 years ago

18. Choose the answer which needs correcting:

From the graphs, we can see that the number of employees who employed by this firm is increasing each year

  A                                 B                                                                     C                                    D

19. Choose the word whose underlined part is pronounced differently from the others.

A.cook                                   B.necessary                          C. decide                              D. cereal

20. Choose the answer which needs correcting:

The cells covering the walls of the stomach will soon be dissolved by the acids if they aren’t constantly replace.

                    A                       B                                                C                                                                       D

21. The injured ____ to the hospital in an ambulance.

A. have taken              B. was taking                          C. were taken              D. were taking

22. After marriage, Mrs. Hoa always keeps good ____ with her mother-in-law.

            A. association              B. relation                               C. friendship               D. relationship

23. In many countries, divorces ____ to rise because of long-standing conflicts.

            A. tend            B. have                                    C. aim                          D. encourage

24. It ____ that the painting is a fake.

A. believed                  B. is believed                          C. is believing             D. was believing

25. Most studies ____ that acupuncture does not reduce nausea and vomiting caused by radiation therapy.

A. are shown               B. were shown                        C. have shown D. have been shown

Choose the best answers to complete the sentences :

1. Nowadays, there is estimated to be more than 2000 acupoints throughout the human body

A. stress                                 B.pressure points                 C. paints                               D. lines

2. Do you know what the saying “ kick a habit ” means ?

A. Wow, She has a good habit                            B. I think it has the same meaning to getting rid of a habit

C. I don’t mean that                                             D. Are you kidding ?

3. I have been given 10 tricks to get rid of my bad habits and ............. them with healthy ones.

A. replace                               B.keep                                  C. nurture                             D. raise

4. The digestive system lets us break down the food we eat and turn it .............. energy.

A. on                                      B.after                                  C. of                                     D. into

5. “The lecturer splits the   4 groups” has the closest meaning to

A. The students are divided into 4 groups                 B. The lecturer divided the students into 4 groups

C. The lecturer is split  into 4 groups of students     D. The lecturer went  into 4 groups of students

6. In the past, it was misunderstand that inner body parts were ............ by the fine needles in practicing acupuncture.

A. touch                                 B.rush                                   C. touched                            D. rushed

7. The ............... system controls the movement and emotion of our body.

A. nerve                                 B.nervous                             C. circulate                           D. generous

8. The heart and blood vessels are parts of the .................. system.

A.certan                                 B.circle                                 C. circulatory                        D. circumstance

9. Only human produce ......................... tears

A.emotional                           B.crocodile                           C. feel                                   D. false

10. To be recognized, this research must offer real evidence. The underlined word has the closest meaning to:

A.knowledge                         B.exist                                  C. condition                         D. proof

Put the word in bracket into the correct form

1. We congratulate James on his well-deserved .................................... to Chief Executive. (promote)

2. This is a great opportunity to ....................................... the reputation of the company. (enhancement)

3. The clock was restored to its ................................... condition. (originate)

4. 1.The low..................................(attend) at the concert was a result of the organizers' carelessness about giving it even more extensive publicity.
5.Another attempt to establish a...................................(last) peace has failed after one of the negotiators refused to sign the treaty.
6.This new situation is more than a/ an.........................................(advantageous) to all the investors. Definitely,it's a chance not to miss.
7.Besides innumerable human victims, the tornado has caused an enormous ..................................(destroy) to the buildings in the area.
8.A sudden..................................(grow) in food prices will certainly bring about violent protests from the population.

Give the correct form of the verbs in brackets:

1. I guess I ( finish ) ........................................................................ my assignment for this semester on time.

2. They have bought a couple of tickets and they ( see ) .............................................. their favorite film at the cinema.

3. Do you know that John has been in hospital ? – No, I don’t. I ( visit ) ...................................... him tomorrow.

4. Mai: This bag is too heavy ! – Nam: Don’t worry. I ( carry ) ....................................... it for you.

5. I think that the number of people who are ( decrease ) .................................. dramatically next quarter.

6  The same discount ( offer ) ............................................ by this shop every month.

7. Human body ( can / support ) ................................................... by a spine

8. A box full of chocolate ( send ) ........................................ to him yesterday.

9. More than 10 pages ( type ) ................................................ so far.

10. Every day, the dishes ( wash ) ............................... by Jane but today the washing-up ( do ) ............................. by Jame.

 Lúc 7h30 sáng, xe ô tô một khởi hành từ A chuyển động thẳng đều về B với36km h. Nửa giờ sau, xe ô tô hai chuyển động thẳng đều từ B đến A và gặp nhau lúc 8 giờ 30 phút. Biết A cách B 72 km. Chọn chiều dương là từ A đến B ,gốc toạ độ tại A, gốc thời gian lúc xe ô tô một khởi hành.Tìm vận tốc của xe ô tô thứ hai.