题目内容：

Being sociable looks like a good way to add years to your life. Relationships with family, friends, neighbors, even pets, will all help, but the biggest longevity (长寿) seems to come from marriage. The effect was first noticed in 1858 by William Farr, who wrote that widows and widowers (鳏夫) were at a much higher risk of dying than the married people. Studies since then suggest that marriage could add as much as seven years to a man’s life and two to a woman’s. The effect can be seen in all causes of death, whether illness, accident or self-harm.

Even if the chances are all against you, marriage can more than compensate you. Linda Waite of the University of Chicago has found that a married older man with heart disease can expect to live nearly four years longer than an unmarried man with a healthy heart. Similarly, a married man who smokes more than a pack a day is likely to live as long as a divorced man who doesn’t smoke. There’s a flip side, however, as partners are more likely to become ill or die in the couple of years following their husband or wife’s death, and caring for your husband or wife with mental disorder can leave you with some of the same severe problems. Even so, the chances favor marriage. In a 30-year study of more than 10,000 people, Nicholas Christakis of Harvard Medical School describes how all kinds of social networks have similar effects.

So how does it work? The effects are complicated, affected by socio-economic factors, health-service provision, emotional support and other more physiological mechanisms(生理机制). For example, social contact can promote development of the brain and immune system, leading to better health and less chance of depression later in life. People in supportive relationships may handle stress better. Then there are the psychological benefits of a supportive partner.

A life partner, children and good friends are all recommended if you aim to live to 100. The overall social network is still being mapped out, but Christakis says: "People are inter-connected, so their health is inter-connected."

1.It can be inferred from the context that the "flip side" (Para. 2) refers to _________.

A. the disadvantages of being married

B. the emotional problems arising from marriage

C. the responsibility of taking care of one's family

D. the consequence of a broken marriage

2.What does the author say about social networks?

A. They have effects similar to those of a marriage.

B. They help develop people's community spirit.

C. They provide timely support for those in need.

D. They help relieve people of their life's burdens.

3.What can be inferred from the last paragraph?

A. It's important that we develop a social network when young.

B. To stay healthy, one should have a proper social network.

C. Getting a divorce means risking a reduced life span.

D. We should share our social networks with each other.