根据下列文章,请回答 51～65 题。
A Special Clock
Every living thing has what scientists call a biological clock that controls behavior．The biological clock________(1)plants when to form. flowers and when the flowers should open．It tells insects when to________ (2)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________ (3)the actions of some biological clocks．Scientists recently found。for example。that a tiny animal changes the color Of its fur because of the________ (4)of hours of daylight．In the short________ (5)Of winter，its fur becomes white．The fur becomes gray brown in ________ (6)in the longer hours of daylight in summer．
Inner signals control other________ (7)clocks；1German scientists found that Some kind of internal clock seems to Order birds to begin their Long migration ________ (8)twice each year．Birds ________ (9)from flying become restless when it is time for the trip，________ (10)they become calm again when the time of the flight has ended．
Scientists say they are beginning to learn which ________ (11)of the brain contain biological clocks．An American researcher Martin Moorhead，said a small group of cells near the front of the brain ________ (12)to control the timing of some of our actions．These________ (13)tell a person when to wake，when t0________(14)and when 10 seek food．Scientists say there probably are other biological clock cells that________(15)other body activities．
第 51 题

A. says
B. asks
C. tells
D. talks