根據(jù)短文內容，從方框中選擇適當?shù)倪x項完成短文。（有兩個選項是多余的）

   Today a lot of people work in offices．They __1__ most of their time indoors．In the evenings they usually watch TV or __2__ newspapers．In order to keep __3__ good health, they know they have to exercise．

    Exercising in important．Doctors __4__ it is good for us．It makes us strong．Children who often exercise are more alert（機靈）．This means they do better in tests and schoolwork than those who don’t __5__ exercise．

    There are many ways to exercise．You can walk, run, swim, skate, or play ball games．Make sure you do more exercise in sports __6__, you must like what you’re doing．Exercise enough, but not __7__．It’s best to exercise twice each week．Thirty minutes each time is enough．Try to exercise many __8__ of things that you feel right for you．

   You can exercise in gyms．There are a lot of equipments（儀器）there．The equipment will help exercise your arms, legs and __9__ parts of your body．Some people buy equipments for their homes．But it is expensive．

   Exercising may be __10__．But you can exercise  together with your friends in a gym．You can feel very happy．

The keys to reaching or staying at a healthy weight are regular exercise and good eating habits. Teens should get 60 minutes or more of physical activity a day. Note the word “activity”. As long as you’re getting your body moving, it doesn’t have to mean doing difficult exercise or going to the sports hall every day. All that matters is that each week you get the right balance of activity, including aerobics (有氧運動), strength building, and flexibility (柔韌) exercise. Make exercise a habit by arranging some time every day.

On days when you have soccer practice or an aerobics class, you may have no trouble exercising for an hour or more. But most of us are busy, and 60 minutes a day for exercise seems like a lot of time. The good news is that it’s OK to divide it into shorter exercise breaks throughout the day.

Just as you might have a healthy snack to stop yourself from getting hungry, exercise snacks can keep energy levels high. So get up 15 minutes early and do some stretching (伸展) activity. Walk fast or run slowly for 15 minutes after lunch. Do the same thing after school — or walk or bike home. Add to that taking the stairs, PE class, and walking between classes during the day, and you’ve probably reached your 60 minutes.

Here are five simple ways to make an exercise lifestyle change:

1.The writer thinks many people probably misunderstand the word“activity” to be “_______”.  

2.When exercising, the most important fact is ________.

3.The author advises dividing activity into shorter exercise breaks because ___.

4.What’s the best title for this passage?