Ở địa phương bạn, năng lượng gió và năng lượng nước chyar đã được sử dụng trong những việc gì?

Một người đứng cách bức tường 20 m thì khi nói to, người đó có thể nghe được tiếng vang không? Tại sao? Biết vận tốc truyền âm trong không khí là 340 m/s.

Thế nào là phương pháp hình chiếu vuông góc?

Lập phương trình hóa học của các phản ứng sau đây:

Chọn câu đúng:

A. H₂O₂ chỉ có tính oxi hóa

B. H₂O₂ chỉ có tính khử

C. H₂O₂ không có tính oxi hóa lẫn tính khử

D. H₂O₂ vừa có tính oxi hóa, vừa có tính khử

Mark the letter A, B, c, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

Little House on the Prairie, a successful television program, was adapted from a series (A) of books by a woman whose (B) life was similar to that of (C) the character called by name (D) Laura.

A. series

B. whose

C. that of

D. by name

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks from 24 to 28.

A surprising number of popular spectator sports, for example football or baseball, (24)______ in Europe or the USA in the nineteenth century. This did not happen by chance. It was the (25) ______ of changes in the way people lived in those places at that time. Until then, more people lived In the country than in towns. They worked in small groups and had no regular time off. All this changed with the growth of factories and industry in the nineteenth century, first in Europe and (26) ______. In the USA. For the first time, most people began to live in towns, and they found themselves with regular free time. They had more leisure time than ever before. This resulted in the need for organized entertainment. Suitable games developed or were invented, typically team games, in which the crowd could (27)______ sides and become involved. This gave people some of the entertainment they need in their free time. The recent explosion in TV, with the introduction of satellite and cable channels, has caused an increase in (28) ______ for sports as entertainment. The money TV has broughtto games such as football, tennis and baseball means that spectator sports will certainly go on playing an important part in our lives.

Điền vào ô trống 24

A. started 

B. stemmed 

C. appeared 

D. came