A Biological Clock Every living thing has what scientists call a biological clock that controls behavior. The biological clock tells _____1___ when to form flowers and when the flowers should open1. It tells _____2____ when to leave the protective cocoon and fly away, and it tells animals and human beings when to eat, sleep and wake.
* }" N! i8 Q* \7 Y: q/ M Events outside the plant and animal _____3_____ the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur ____4_____ the number of hours of daylight. In the short ____5___ of winter, its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight summer.9 _0 J0 V" C! Z- ^# k
Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration _____6____ twice each year. Birds _____7_____ flying become restless when it is time for the trip, ____8___ they become calm again when the time of the flight has ended.* B5 c H8 M! A0 p/ P: p, f
Scientists say they are beginning to learn which ____9____ of the brain contain biological clocks. An American researcher, Martin Moorhead, said a small group of cells near the front of the brain ____10____ to control the timing of some of our actions. These ____11____ tell a person when to _____12_____, when to sleep and when to seek food. Scientists say there probably are other biological clock cells that control other body activities.1 u$ \& {/ [2 g! x
Dr. Moorhead is studying _____13____ 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. _____14____ 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 ____15____ understanding could cut sickness and accidents at work and would help increase a factory's production.
0 L) y" m4 j# h6 v8 r- ], Z 1. A scientists B humans C plants D animals
9 D7 a. r8 G3 C A/ u 2. A insects B birds C fish D snakes
t3 I% q; c) G+ v2 L 3. A effect B affect C effected D affected中 华 考 试 网
; G, I S9 R$ b: Z 4. A because B for the reason that C because of D since
3 p- Q8 t' f6 e" H! h8 v/ X 5. A months B days C minutes D weeks+ v7 Q+ S! S3 Y; [2 E
6. A flight B fly C movement D transportation
H4 N8 h9 H/ R 7. A prevented from B ordered by C helped by D intruded on2 P' v8 w) W7 W
8. A and B but C therefore D however
9 k/ V+ M8 w* X- k 9. A portions B parts C sections D kinds# \ u- W. b8 ^% n, \+ f
10. A try B tries C seem D seems外语学习网
6 K$ W+ K, k l1 ?$ G/ u 11. A things B parts C cells D actions
! l1 P5 M9 X4 W+ U; F3 W( s8 X: K: } 12. A awaken B wake C awakening D wake-up
* u2 ] ~! i7 S 13. A how B why C where D what( B" Z, L* {, t5 m& Q* e
14. A We B It C They D You1 J' k7 q/ ^) Q k
15. A so B with C such D if0 _7 B% C# w; O' ?) C5 `1 R
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