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  3. Imagine an animal that becomes frozen in cold weather. Then, when it gets warmer, the animal simply unfreezes and goes back to i

Imagine an animal that becomes frozen in cold weather. Then, when it gets warmer, the animal simply unfreezes and goes back to i

admin2015-01-31  35
问题     Imagine an animal that becomes frozen in cold weather. Then, when it gets warmer, the animal simply unfreezes and goes back to its normal life. Although this may sound like something from a science-fiction movie, it is exactly what happens to the wood frog over winter and spring. When winter begins, the frog, which is found throughout much of Canada, buries itself in leaves and dirt. As the ground begins to freeze, so does the frog’ s body.
    Normally, if a living creature is frozen, the cells inside its body are destroyed, leading to death. How, then, does the wood frog survive? The secret lies in the fact that although the water between the cells in the frog’ s body becomes frozen, the water inside the cells does not freeze. Before the winter begins, the frog stores starch in its body. As the weather gets colder, the drop in temperature causes the frog’ s body to change this starch into glucose. This glucose, in turn, lowers the temperature at which the liquid inside the frog’s cells freezes. As a result, the cells do not freeze even at very low temperatures, allowing the frog to stay alive. Some wood frogs stay in this frozen state— with their hearts stopped completely—for months without harm.
    Now researchers are hoping to adapt the wood frog’ s secret to help them preserve human organs for transplants. Currently, after organs are removed from a donor’ s body, they are packed in a special liquid and kept very cold. However, they cannot be frozen because the ice would damage the cells in the organs. For this reason, the organs must be used quickly. If doctors had a way to preserve organs longer, they would have more time to find the best matches among people waiting for organ transplants.
    There is still a lot about the wood frog that scientists do not understand. They still have to work out, for example, exactly how the frog is able to unfreeze itself and what actually restarts the frog’s heart when the weather becomes warmer. What is clear, however, is that lessons learned by studying this tiny creature could be of great benefit to humans in the near future.
What effect does the glucose produced in the wood frog’ s body have?
选项 A、It stops the water in the frog’ s cells from freezing in cold weather.
B、It lowers the temperature in the spaces between the frog’ s cells.
C、It causes the frog’ s cells to produce more starch.
D、It allows the frog’ s cells to produce more water.
答案A
解析 细节题。短文第二段中间指出This glucose，in turn，lowers the temperatureat which the liquid inside the frog’s cells freezes．意为这种葡萄糖可以降低wood frog细胞液体结冰的温度。由此可知这种葡萄糖使细胞里的水不会结冰，故选A。
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大学英语四级

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