21. If you don't rest, you will be ill.

     ->  Unless you rest , you will be ill.

 22. This tree won't grow if there no water.

     ->  Unless there is water, this tree won't grow.

 31. A. Doing

IV/ 1. I listen to music every night.

      2. They go to school every day.

      3. We get up at 5 every morning.

      4. You live in a big city.

      5. Nga and Lan brush their teeth.

      6. Nam and Ba wash their face.

      7. I have breakfast every morning.

      8. Na has breakfast at 6 o’clock.

      9. Every morning, Ba gets  up.

    10. He brushes his teeth.

    11. Then he washes his face.

    12. Next he has breakfast.

    13. Finally, he goes to school.

    14. Nga does homework every day.

    15. Linh watches television at night.

    16. She often misses her parents.

    17. He always studies English.

    18. Loan has dinner at 7pm.

    19. I have dinner at 6 pm.

    20. They do homework at 2 pm.

    21. You watch movies at 8.30.

    22. We study English on Mondays.

    23. Hoa has  English on Tuesday.

    24. Lan opens the door.

    25. Hoa closes the window.

    26. The teacher comes in.

    27. The students stands up.

    28. They sit down.

    29. My father lives in a big city.

    30. Your friend goes home at 4 pm.

    31. Nam’s father gets up at 4 o’clock.

    32. Hoa goes to school by bus.

    33. This is Mai. She is twelve years old. She is a student. She lives in a big city. She is in grade 6. She gets up at 6 o’clock every morning. She washes her face at 6.10. She has breakfast at 6.15. She goes to school at 6.30.

 A) PTK của BaCl2:   137 + 35.5 * 2 = 208 đvC

      PTK của FeCH:    56 + 12 + 1 = 69 đvC

      PTK của FeCl₃:     56 + 35.5 * 3 = 162.5 đvC

      PTK của CaCH:     40 + 12 + 1 = 53 đvC

      PTK của NaCl:       23 + 35.5 = 58.5 đvC

      PTK của HCl:         1 + 35.5 = 36.5 đvC

 B) PTK của CaCO₃:    40 + 12 + 16 * 3 = 100 đvC

      PTK của Na₂CO₃:   23 * 2 + 12 + 16 * 3 = 106 đvC

      PTK của CuCO₃:     64 + 12 + 16 * 3 = 124 đvC

      PTK của H₂CO₃:      1 * 2 + 12 + 16 * 3 = 62 đvC    

 Số thập phân có mười lăm đơn vị, bảy phần trăm viết là: 15,07

 II. 1.  We are staying at my cousin's house in Vung Tau .

     2. Do they have the right things for the kitchen ?

     3. Where do you live ,Phong ?

     4. Where does your uncle live ?

     5. How many rooms are there inthe hotel ?

     6. There aren't any chairs in the kitchen .We need five chairs.

  I. 1. A 

     2. B

     3. B

     4. B

     5. B

     6. B

     7. B 

     8. A

     9. D ( have a bath: đi tắm)

    10. A

    11. D

    12. A

    13. B

    14. D

    15. C

    16. D

    17. B

    18. B

    19. A

    20. B

 IV/  1. Vietnam is hotter than Sweden.

       2. Saigon is noisier than Dalat.

       3. There are many motorbikes in the town.

       4. Planes are faster than trains.

       5. The air in the city is more polutted than the air in the countryside.

       6. Is there a theatre in your neighbourhood ?

 1. Is John eleven years old?

 2. Mary and Jane are at the park.

 3. Are your brothers on holiday?

 4.  Your cat is lovely.

 5. I am at school.

 6. They are doctors.

 7. My favourite colour is blue.

 8. You are good at English.

 9. Are there any restaurants near here?

 10. What are your hobbies? 

 11. Why is the Korean pop music so popular?

 12. Is your mother a housewife?

      How much is a can of Coke?

 2. Nobody else in my class is as tall as Lien.

       Lien is the tallest in my class.

 3. These notebooks have two hundred pages.

       There are two hundred pages in these notebooks.