根据短文内容及首字母提示，填写所缺单词，使短文意思完整，每空限一词。(10分)

Teenagers live very busy lives now and often forget to think about their diets and exercise．The truth is, healthy eating along with regular exercise is the only way to k  1.       fit．

During your teenage years, it is important to give your body the energy it needs．Teenage g2.      need about 2,200 calories a day and boys need a bit m  3.      —doctors suggest 2,800 for teenage boys．50% of your calories should come f 4.       rice, bread, vegetables and fruit．You also need to drink a lot of water, 6 to 8 glasses a day．Drinking e  5.   water will improve your skin and give you healthy hair．

E  6.       is something that can help to make you look good, feel good and be healthy．Experts(专家) suggest that teenagers s  7.       at least 30 minutes exercising, five times a week．W 8.       you exercise, your body produces something that makes you feel r  9. ．It can even help you sleep better at night and let you pay more a  10.  when you study!

缺词填空  先通读下列短文，掌握其大意，然后根据短文内容和所给首字母，在空格内填入一个适当的词，使短文意思完整。所填单词在题后横线上必须完整写出（本大题共6分，每格0.5分）

Suppose you are reading a book. Suppose you suddenly close your eyes, can you still see the book? "Of course not." you will say. But can you tell why? You would p__1. say, "When I close my eyes, my e__2.___ cannot get out of my eyes to get to the book." Many others might give an explanation(解释) very much like the above . But this explanation is w__3.___.

      You cannot see any object if light from that object doesn’t get into your eyes. Some of the things you see give off light of their own.

      The sun, the star, a lighted lamp are examples that can be seen by their own light. S__4.__ things are luminous(发光的). Most of the things you see are not giving off light of their own. They are simply reflecting(反射) light that falls on them from the sun or some other luminous bodies. The moon, for example, doesn't give off any light of i__5._ own. It's non-luminous. You see it because sunlight falls on it and some of it reflects in your d__6.__. So moonlight is only second-hand sunlight.

      When you look at a book, it sends to your eyes some of the light which falls on it, and you see the book. If light could be kept out from w__7.__ you are, so that there would be no light for the book to reflect, then you could not see the book e__8.__ with your eyes wide open.

      Light travels so fast that the time it t___9.__ from the book to your eyes is so s___10._ as if there was none at all. Light r___11.__ us from the moon, which is about 380,000 kilometers away, in only a little more than a s__12.__.