题目内容：
回答题：A Special Clock Every living thing has what scientists call a biological clock that controls behavior. The biological clock________（51） plants when 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 tells animals and human beings when to eat, sleep and wake.
Events outside the plant and animal__________（53） the actions of some biological clocks . 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.
Inner signals control other _________（57） clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration_________（58） twice each year. Birds _________（59） from flying become restless when it is time for the trip, _________（60） they become calm again when the time of the flight has ended.
Scientists say they are beginning to learn which _________（61） of the brain contain biological 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 when to wake, when to _________（64） and when to seek food. Scientists say there probably are other biological clock cells that __________（65） other body activities. A．says
B．asks
C．talks
D．tells
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