首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to【C1】______ flowers
Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to【C1】______ flowers
admin
2010-10-28
31
问题
Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to【C1】______ flowers and insects when to leave protective cocoon (茧)and fly away. And it tells animals and human beings when to【C2】______ , sleep and seek food. It controls our body temperatures, the【C3】______ of some hormones and even dreams.
Events 【C4】______ the plant and animal affect its actions. Scientists recently found that a tiny animal called Siberian hamster changes the color of its【C5】______ because of the number of hours of【C6】______ In shorter days of winter its fur becomes white. The fur becomes gray-brown in longer【C7】______ of daylight in summer.
【C8】______ signals control other biological clocks. German scientists found that some internal one seems to order birds to begin their【C9】______ flights two times each year. Birds prevented from flying become【C10】______ when it is time for the trip.【C11】______ they become calm again when the time of the flight has ended. A mix of outside and internal events controls some biological clocks; such things as heartbeat and the daily change from sleep to walking take place because of both external and internal signals.
Scientists are beginning to learn【C12】______ parts of the brain contain the biological clocks. A researcher at Harvard University, Dr. Martin Moore Ede, said a small group of cells near the front of the brain seemed to control the【C13】______ of some of our actions. Probably there are other cells to control other body activities. He is studying【C14】______ they affect the way we do our work. Most of us have great difficulty if we【C15】______ often change to different work hours.【C16】______ can take many days for a human body to【C17】______ a major change in work hours. Industrial officials should have a better【C18】______ of biological clocks and how they affect workers. He said such an understanding could【C19】______ sickness and accidents at work, and would help increase【C20】______ .
【C15】
选项
A、may
B、can
C、must
D、might
答案
C
解析
考查情态动词 。情态动词的使用应该参照语境。人们更换工作时间一般是迫不得已而为之,因此只有等到必须做的时候才会更换。must表示“必须”,所以C项正确。
转载请注明原文地址:https://kaotiyun.com/show/nrz7777K
0
大学英语六级
相关试题推荐
Althoughthefactthattodayvirusesareknownto【S1】______causecancerinanimalsandincertainplants,tha
Althoughthefactthattodayvirusesareknownto【S1】______causecancerinanimalsandincertainplants,tha
Althoughthefactthattodayvirusesareknownto【S1】______causecancerinanimalsandincertainplants,tha
Althoughthefactthattodayvirusesareknownto【S1】______causecancerinanimalsandincertainplants,tha
Livingisrisky.Crossingtheroad,drivingacar,flying,swallowinganaspirintabletoreatingachickensandwich--theycana
Livingisrisky.Crossingtheroad,drivingacar,flying,swallowinganaspirintabletoreatingachickensandwich--theycana
Livingisrisky.Crossingtheroad,drivingacar,flying,swallowinganaspirintabletoreatingachickensandwich--theycana
Weallscreamforwaterwhenthirsty,butdoyouknowinveryhot,dryweather,plantsalsomake【B1】______soundsasiftheya
Weallscreamforwaterwhenthirsty,butdoyouknowinveryhot,dryweather,plantsalsomake【B1】______soundsasiftheya
Weallscreamforwaterwhenthirsty,butdoyouknowinveryhot,dryweather,plantsalsomake【B1】______soundsasiftheya
随机试题
双手触诊脾脏时,可让患者
男,56岁,左小腿轻度肿胀,有多条蚓状血管团,其内有硬结,症状逐年加重,如不进行治疗,其最严重的后果是
石菖蒲的组织结构中有
下列不属于癌前疾病或癌前病变的是
患者,男性,54岁,劳累后感心悸。查脉搏,每隔1个正常搏动后出现2次过早的搏动。判断此脉律为
下列选项中完全包括不动产投资的类型的选项是()。Ⅰ.酒店投资Ⅱ.地产投资Ⅲ.商业房地产投资Ⅳ.工业用地投资
牛顿曾经说:“自然界不做无用之事。只要少做一点就成了,做多了却无用,因为自然界喜欢简单化,而不爱用多余原因来夸耀自己。”人却恰恰相反,常做自认为有用之事,事实却证明常常无用。白岩松常引用的例子:8所名牌大学的毕业生,其中2名博士、5名硕士,还有2
下列哪项不是城市生态系统物质循环的特点?()
表象可以为想象提供素材是因为表象具有()
A、Thetotalofhisorderis$17.90.B、Thephonenumberis340-1870.C、Theaddressis1340North16East.D、Thecustomerwantsa
最新回复
(
0
)