题目内容：

    Playing tennis regularly could help keep people off death, but football, rugby and running may not help people to live longer, a study suggests.

A study followed more than 80,000 people for an average of nine years to find out if certain sports protected them against early death. It found that people who played racket sports regularly were the least likely to die over the study period, reducing their individual risk by 47 percent compared with people who did no exercise. Swimmers also reduced their chance of death by 28 percent, aerobics (有氧运动) fans by 27 percent and cyclists by 15 percent. Yet running appeared to have no impact at all on dying early, and neither did playing football or rugby.

Scientists say the difference may lie in the social aspect which goes alongside sports like tennis and squash (壁球), which often involve clubs and organized activities outside of the game. It means that people often have larger social net-works and tend to keep up activities into later life, both of which are proven to be good for health.

In contrast, people who play team sports often do not move onto a new sport once their teams break up for family, or injury reasons. They become watchers rather than participants in their chosen activity.

The researchers found that playing racket sports was associated with a 56 percent lower risk from heart death. Similarly, swimmers lowered their heart disease or stroke risk by 41 percent, and people who took part in activities like aerobics, dance or gymnastics lowered their risk by 36 percent. But again running, football and rugby had no significant impact on heart deaths.

However, other experts argue that this study must not be misinterpreted as showing that running and football do not protect against heart disease. In this study both runners and footballers had a lower rate of death from heart disease.

1.Which sport has hardly any impact on protecting people against early death?

A.Cycling. B.Swimming.

C.Rugby. D.Tennis.

2.According to the study, which makes a big difference in keeping healthy?

A.Playing basketball with their friends occasionally.

B.Watching football games every day.

C.Taking up gymnastics and joining a club.

D.Doing running in the park every day.

3.What is considered more important to people's health?

A.Social networks. B.Staying at home.

C.Physical examinations. D.Setting up families.

4.What is the main idea of the text?

A.Thousands of people participated in a 9-year research.

B.Study finds playing tennis helps people live longer.

C.It is wrong to say running has no impact on heart disease.

D.There are differences between racket sports and team games.