科目：高中英语 来源： 题型：051
Living things can regulate their own activities in such a way that they fit into the rhythms (节奏) in nature. For example, plants consume (大量吸收) sunshine during the day and do most of their breathing at night. Small animals which live in very hot regions remain deep in their holes during the heat of the day and only come out at night to obtain food. These rhythmic patterns of activity in living things can be called biological clocks.
Scientists have discovered some very interesting facts about biological clocks. Their most important discovery is that although biological clocks approximately (近似地) correspond to the rhythms of day and night, light and darkness, they do not always depend on them. Many biological clocks are independent. How can this be proved? It can be proved by showing that a biological clock will continue to operate even when its surroundings are changed so that it can no longer respond to alternating periods of lights and darkness.
We will take the crab (蟹) as an example. This animal is a living clock. It indicates (指出) the time by the color of its skin, which is dark during the day and lighter in color during the night. The daytime darkness of the crab's skin, which prevents its enemies from noticing it and also prevents the crab from getting too hot, is repeated every 24 hours. The alternating colors of the skin appear to follow the alternating rhythm of day and night. How can we prove the statement that crab is an independent clock which creates its own rhythm, its own time? Perhaps it only responds to sunlight, by growing darker when in contact with sunshine and growing lighter in color when the sun sinks behind the horizon (地平线)?
To answer this question, biologists did a simple experiment. They kept the crab in a dark room at a constant temperature for two months. They found that the skin of the crab continued to change color according to the same 24-hour rhythm, following the movements of the sun outside. In this way they proved that the crab's biological clock was independent of events in its natural surroundings. It was not just a series of responses to external events.
1. Biological clocks in living things are——.
A. natural rhythms
B. the alterations of day and night
C. living thing's activities corresponding to some natural rhythms
D. the repetition of activities of living things
2. The author compares a crab to——.
A. a biological clock B. an example of biological clock
C. a living clock D. a model of biological clocks
3. A crab is an example of biological clocks in living things because it
A. looks like clocks
B. has dark skin
C. creates its own time
D. alternates color of its skin to follow the alternating rhythm of day and night
4. The colors of the crab's skin can
A. indicate the time
B. prevent its enemies from noticing it
C. prevent it from getting too hot
D. do all the above
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科目：高中英语 来源：学习高手必修三英语北师版 北师版 题型：055
As the sun sinks lower, shadows of the tower spread across the courtyard．
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科目：高中英语 来源： 题型：
_______ the sun sinks lower, shadow spread ________ the courtyard.
A. When; through B. When; across C. As; through D. As; across
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科目：高中英语 来源： 题型：
the sun sinks lower, shadow spread the courtyard.
A．When; through B．When; across C．As; through D．As; across
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