Read the passage, and choose the best answer.

Good manners are a treasure to the people who possess them, as well as to the community they live in. Manners are taught, learnt, and passed from generation to generation.

Even hundreds of years ago, children were taught to behave responsibly. They learnt to respect seniority. When they passed an object to another person, they had to use both hands. When they entered a room, they had to bow and greet the oldest person first. Boys learnt to work hard to support their families. Girls learnt to do housework, and to take care of others. Loyalty and honesty were highly appreciated. When they made a mistake, they would not let another person be punished for it. That would be cowardly and mean. They were taught that families were strong, and everybody should stick together in adversity. (tai họa, nghịch cảnh)

Fortunately, many of these values have been well preserved. They have contributed to making the unique Vietnamese culture, and strengthening our society.

What contributed to making the unique Vietnamese culture?

A. tradition

B. generations

C. good manners

D. seniority

A. khả năng tích điện của tế bào.

B. khả năng truyền điện của tế bào.

C. khả năng phát điện của tế bào.

D. chứa các loại điện khác nhau

Chỉ ra công thức đúng của định luật Cu-lông trong chân không.

 A.  F = k q 1 q 2 r 2

 B.  F = k q 1 q 2 r

 C.  F = k q 1 q 2 r 2

D . F = q q q 2 kr