1. Would you mind if I help you to put the chair away?
2. He had his car repaired yesterday.
3. Lan is the most intelligent person in my class.
4. That exercise is less difficult than this one.
5. She enjoys collecting stamps.
6. My book is less interesting than hers.
7. She entered without knocking at the door.

1. Tam is the tallest person in my class.
2. My mother can cook better than me.
3. Jack can play tennis better than him.
4. You spent more money than I did.
5. This book is not as expensive as it seems.
6. No one in his class is taller than him.
7. No other films are as interesting as this one.
8. Japanese cars are the most expensive in the world.
9. That exercise is not as easy as this one.
10. Jack doesn't drive as carefully as he does.
11. He can play better than anyone else in the group.
12. This hotel is the most comfortable in the city.
13. The Pacific Ocean is larger than any other ocean in the world.

1. My father is the oldest in my family.
2. Tam is the tallest in my class.
3. I don't cook as well as my mother.
4. Jack can play tennis better than him.
5. He can play better than anyone else in the group.

1. B. My friend arrived earlier than I expected.
2. C. No one in my class is as intelligent as Hoang.
3. A. Jack is a less careful driver than Peter.
4. B. The books in English are more expensive than those in Chinese.
5. A. That film is more interesting than this one.
6. A. The toy dog is the same price as the toy cat.
7. A. Your mother is more kind-hearted than anyone.
8. C. Other oceans in the world are larger than the Pacific one.
9. C. My book is cheaper than yours.
10. B. That compass is cheaper than this compass.
11. C. Of all the soups I have ever eaten, his chicken soup is the best.
12. C. The smaller the houses are, the cheaper they are.
13. A. Jane's sister doesn't cook as well as her.
14. B. No other country in Asia is as large as China.
15. C. The villa painted in white is more beautiful than the villa painted in pink.
16. A. No one in my class is more beautiful than Lan.
17. A. The toy dog is the same price as the toy cat.
18. D. Mr. Thomson is much richer than anyone else I know.
19. D. She is the prettiest girl I have ever met.
20. B. My sister is the tallest student in the class.

7. Ba who likes playing the guitar lives on Trang Tien Street.

8. Mount Pinatubo which is a volcano in the Philippines erupted in 1991.

9. It snowed in Lang Son, which is on the Ky Cung River, in the winter of 2002.

10. Venus which is closet to the Earth is a planet.

Lượng mưa và lớp phủ thực vật ở châu Phi có mối quan hệ tương hỗ với nhau :

\(-\) Lượng mưa ít thì lớp phủ thực vật nghèo nàn , thưa thớt.

\(-\) Lượng mưa nhiều thì lớp phủ thực vật rậm rạp , xanh tốt.

Tần số là số dao động trong 1 giây. 

Đơn vị đo tần số là Héc ( Hz ).

Âm phát ra càng cao khi tần số dao động càng lớn.