短文填空。(每空2分，共16分)
根据下面短文内容，在空格处填上一个恰当的词，使短文完整、通顺。
Everyone knows that exercise is important. We all need to exercise. Doctors say it is good     us. It    your heart and body strong. Children who often exercise are more alert（灵活）. That means they do  in tests and schoolwork than those who don’t exercise.
They are many      to exercise. You can walk, run, swim, skate, or play ball games. Make sure you exercise in the following ways: You have to like what you are doing. Exercise enough--- but not too much. It’s best to exercise twice  week. Thirty minutes each time is enough. Try all    of sports until（直到）you find one, two or even three sports that feel right for you.
You can exercise at fitness centers(健身中心). They have a lot of equipment（设备）there. The equipment will help exercise your arms, legs and     parts(部分) of your body to make you     . Some people buy equipment for their homes. But it’s very expensive.