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第六部分 完形填空  （每题1分，共15分） 
阅读下面的短文。短文中有15个空白，在文章的后面，每一个空白都列出了四个备选答案。请根据文章的内容选择合适的词或短语填在空白处。 
  
A Biological Clock 
Every living thing has what scientists call a biological clock that controls behavior. The biological clock tells _________when to form flowers and when the flowers should open1. It tells _________ when to leave the protective cocoon and fly away, and it tells animals and human beings when to eat, sleep and wake. 
  Events outside the plant and anima __________the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur________ the number of hours of daylight . In the short _________ of winter , its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight in summer. 
  Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration __________ twice each year. Birds __________ flying become restless when it is time for the trip, ___________ they become calm again when the time of the flight has ended. 
  Scientists say they are beginning to learn which ____________ of the brain contain biological clocks. An American researcher, Martin Moorhead, said a small group of cells near the front of the brain __________to control the timing of some of our actions. These _________ tell a person when to ___________ , when to sleep and when to seek food. Scientists say there probably are other biological clock cells that control other body activities. 
  Dr. Moorhead is studying _________ our biological clocks affect the way we do our work2. For example , most of us have great difficulty if we must often change to different work hours. __________can take3 many days for a human body to accept the major change in work hours . Dr. Moorhead said industrial officials should have a better understanding of biological clocks and how they affect workers. He said ________ understanding could cut sickness and accidents at work and would help increase a factory’s production.
词汇： 
biological  adj. 生物（学）的    migration   n.迁徙 
insect      n.昆虫                           restless    adj.焦躁不安的 
cocoon     n.防护卵袋，茧          contain    v.含有 
fur        n.软毛                              cell       n. 细胞 
  
注释： 
１、  句中谓语动词tells 的宾语有两部分组成。 第一部分是when to form flowers, 是带疑问浮词的动词不定式，第二部分是when the flowers should open, 是名词从句。从修辞上说，两者有些不平衡。 
２、  …the way we do our work 可以理解为the way in which we do our work 或the way that we do our work. 实际上，三种说法都成立。如：He speaks English the way the English people do.  I don’t understand the way in which he dealt with the matter. 
３、  take 作“花费，花去”解时可用于几种不同的句型： 
It will take me five days to complete the work. 
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