题干

“扳手腕”是中学生课余非常喜爱的一项游戏。如右图,甲、乙两同学正在进行“扳手腕”游戏,下列关于他们的手之间的力,说法正确的是                    (    )

A:甲扳赢了乙,是因为甲手对乙手的作用力大于乙手对甲手的作用力

B:只有当甲乙僵持不分胜负时,甲手对乙手的作用力才等于乙手对甲手的作用力

C:甲、乙比赛对抗时,无法比较甲手对乙手的作用力和乙手对甲手的作用力的大小关系

D:无论谁胜谁负,甲手对乙手的作用力大小等于乙手对甲手的作用力大小

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答案(点此获取答案解析)

D

同类题3

      Without proper planning, tourism can cause problems. For example, too many tourists can crowd public places that are also enjoyed by the local people of a country. If tourists create too much traffic, the local people become unhappy. They begin to dislike tourists and to treat them impolitely. They forget how much tourism can help the country's economy(经济). It is important to think about the people of a destination country and how tourism affects them. Tourism should help a country keep the customs and beauty that attract tourists. Tourism should also advance(推进) the well-being (health and happiness) of local people.
      Too much tourism can be a problem. If tourism grows too quickly, people must leave other jobs to work in the tourism industry. This means that other parts of the country's economy can suffer.
       On the other hand, if there is not enough tourism, people can lose jobs. Businesses can also lose money. It costs a lot of money to build large hotels, airports, air terminals, first-class roads and other support facilities needed by tourist attractions. For example, a major international-class tourism hotel can cost as much as 50 thousand dollars per room to build. If this room is not used most of the time, the owners of the hotel will lose money.
      Building a hotel is just a beginning. There must be many support facilities as well, including roads to get to the hotel, electricity, sewers to handle waste, and water. All of these support facilities cost money. If they are not used because there are not enough tourists, jobs and money are lost.