第51~65题，每题1分，共15分 1、 A Special Clock Every living thing has whatscientists call a biological clock that controls behavior. The biological clock________(51) plantswhen to form flowers and when the flowers should open. It tells insects when to __________(52)the protective cocoon (防护卵袋) and fly away, and it tellsanimals and human beings when to eat, sleep and wake.Eventsoutside the plant and animal__________(53) the actions of some biologicalclocks . Scientists recently found,for example, that a tiny animal changes the color of its fur because of the__________(54) of hours of daylight. In the short_________(55) of winter, its fur becomes white. The fur becomes gray brown in_________(56) in the longer hours of daylight in summer.Innersignals control other _________(57) clocks. German scientists found that some kindof internal clock seems to order birds to begin their longmigration_________(58) twice each year. Birds _________(59) from flying become restless when it is timefor the trip, _________(60) they become calm again when the time of the flighthas ended.Scientistssay they are beginning to learn which _________(61) of the brain containbiological clocks. An American researcher,Martin Moorhead, said a small group of cells near the front of the brain__________(62)to control the timing of some of our actions. These __________(63) tell a person whento wake, when to _________(64) and when to seek food. Scientists say there probably are otherbiological clock cells that __________(65) other body activities.
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