题目内容：

    Teenagers are often a difficult group.With all those hormones(荷尔蒙)flooding in their bodies，they can be moody，unpredictable，and tend to make uncertain choices.But however confusing their teenage years are，kids can still be generally happy，depending on their lifestyle choices.According to a new research by British scientists，teens who don't smoke，drink only moderately(适度地） or not at all，and who don't eat much junk food are likely to be happier than other teens.

The study looked at 40,000 British families and came up with some interesting findings.For example，kids who never drank alcohol were up to six times more likely to report higher levels of happiness than kids who drank.And teens who smoked were five times less likely to rate high on happiness charts compared to kids who didn't smoke.The same goes for diet and physical activities.The more fruits and vegetables kids eat，and the more hours they spend playing sports，the happier they are.

Now，of course this doesn't mean that not smoking or drinking，and playing sports can guarantee happiness.It could be that kids who have happy character tend to be more active and less addicted to drinking or smoking.And it could equally be the case that kids who are unhappy are more related to drinking，smoking and eating junk food.

Other studies have shown that exercise is a proven way to treat anxiety and depression. Future studies may support the idea that other healthy behaviors，including refraining(克制)from smoking，drinking，and eating too much junk food，can avoid sadness and increase happiness，too.

1.The author develops the second paragraph mainly by________.

A.making comparisons B.providing statistics

C.offering examples D.analyzing causes

2.What can we learn from the text？

A.Not smoking or drinking guarantees happiness.

B.Teens with flooding hormones cannot be happy.

C.Playing sports can decrease teens' unhappiness.

D.Unhappiness can certainly lead to smoking and drinking.

3.Which can be the best title for the text？

A.Ways to treat anxiety and depression

B.Exercise and teenagers' health

C.Teenagers shouldn't drink or smoke

D.Teenagers' lifestyle and their happiness