Teenagers believe anything is possible if thy study hard．But they often forget to think about healthy diets（饮食），enough sleep time and exercise．In fact，these things are really important for them to keep fit．
  It is important for teenagers to get enough energy．Teenage girls need about 2200 calories a day while boys need a bit more-doctors suggest 2800 for teenage boys 50% of their calories should come from healthy food-rice，begetables and fruit．People often say an apple a day keeps the doctor away．Teenagers also need to drink a lot of water，6 to 8 glasses a day．Drinking enough water will improve their skin．
  Teenagers usually need eight to ten hours'sleep at night，but many Chinese teenagers do not get enough sleep．A report shows that without a good night's sleep，teenagers seem to be weaker than they should be．Too much homework is not the only reason why teenagers stay up late．Some watch TV or play computer games late into the night．Teenagers should develop good study habits．So some clever students never study late，but they are able to work well in class．
  Exercise is something that can help them．Experts suggest that teenagers should spend at least 30 minutes exercising a day，five times a week．They will feel relaxed when they exerxise．It can even help them sleep better at night．

46．How many things are important for teenagers to keep fit？    
A.2                    
B.3                  
C.4
47．Half of their calories should come from    ．
A．rice，vegetables and fruit  
B．rice，vegetables and meat 
C．rice，vegetablesand water
48．The last paragraph（段）mainly talks about    ．
A．sleeping better      
B．basic energy      
C．necessary exercise 
49．Which of the following is NOT true？    
A．Boys need much more calories than girls
B．Teenagers need to drink 6 to 8 glasses of water a day
C．Some clever students never study late
50．The passage tells teenagers how to    
A．eat and drink well      
B．study hard    
C．keep fit．

【考点】健康环保类阅读,判断推理,内容归纳

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