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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.
詞彙：
biological adj. 生物（學）的 migration n.遷徙
insect n.昆蟲 restless adj.焦躁不安的`
cocoon n.防護卵袋，繭 contain v.含有
fur n.軟毛 cell n. 細胞
註釋：
１、 句中謂語動詞tells 的賓語有兩部分組成。 第一部分是when to form flowers, 是帶疑問浮詞的動詞不定式，第二部分是when the flowers should open, 是名詞從句。從修辭上說，兩者有些不平衡。
２、 …the way we do our work 可以理解爲the way in which we do our work 或the way that we do our work. 實際上，三種說法都成立。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“花費，花去”解時可用於幾種不同的句型：
It will take me five days to complete the work will take me five days to complete this work will take me five days.
練習：
1. A) scientists B)humans C)plants D)animals
2. A)insects B)birds C)fish D)snakes
3. A) effect B) affect C)effected D) affected
4. A) because B)for the reason that C) because ofD)since
5. A)months B)days C)minutes D)weeks
6. A)flight B)fly C)movement D)transportation
7. A)prevented from B)ordered by C)helped by D)intruded on
8. A)and B)but C)therefore D)however
9. A)portions B)parts C)sections D)kinds
10. A)try B)tries C)seem D)seems
11. A)things B)parts C)cells D)actions
12. A)awaken B)wake C)awakening D)wake-up
13. A)how B)why C)where D)what
14. A)We B)It C)They D)You
15. A)so B)with C)such D)if
