题目内容：

完形填空,阅读下面短文，掌握其大意，然后从各题所给的四个选项中选出一个最佳答案。

Why exercise？

You’ve probably heard countless times how exercise is “good for you”. But did you know that it can ________ help you feel good? Exercise plays a key role in ________ healthy. It can strengthen the bones, heart, lungs and muscles. It can also________ the stress and help you sleep better. Experts suggest that teenagers should get 60 minutes or more of physical ________ each day. Here are some of the reasons:

Exercise benefits（有益）every part of the body, ________the mind. Exercising causes body to produce chemicals that can ________a person feel more peaceful and happier. It can ________ help some people who have mild mental diseases. ________ exercising can help you look better. People who exercise burn more energy and look________ than those who don’t.

In fact, exercise helps people lose ________ and lower the risk of some diseases. Exercising to maintain (保持) a healthy weight decreases a ________ risk of developing certain diseases. These diseases, which ________ found mostly in adults, are becoming more common in teenagers.

Exercise can help a person age well. This ________ not seem important now, but your body will thank you later. Studies have found that weight-bearing exercise, ________ jumping, running and walking, can help people keep their ________ strong.

You may not feel like doing exercise regularly, but why not do it due to the above mentioned reasons from now on?

1.A. quietly       B. actually         C. recently         D. quickly

2.A. staying       B. helping          C. giving          D. looking

3.A. keep          B. reply            C. refuse          D. reduce

4.A. homework     B. activity        C. experiment      D. language

5.A. except      B. plus             C. during          D. including

6.A. help         B. ask              C. tell             D. teach

7.A. already       B. also             C. afterwards       D. almost

8.A. Although     B. Because          C. Unless          D. And

9.A. fatter        B. slimmer          C. taller           D. shorter

10.A. energy       B. weight           C. happiness       D. experience

11.A. people’s    B. person’s        C. humans’        D. mankind’s

12.A. used to do  B. are used to be  C. used to be       D. are used to being

13.A. should       B. must             C. may             D. need

14.A. such as     B. for example     C. the same as      D. so that

15.A. hands        B. bones            C. mouths           D. feet