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  3. Since the beginning of history, man has been attracted by the idea of living forever, of winning the fight against death and dis

Since the beginning of history, man has been attracted by the idea of living forever, of winning the fight against death and dis

admin2016-08-30  51
问题     Since the beginning of history, man has been attracted by the idea of living forever, of winning the fight against death and disease. So far, this has only remained a dream, though a very powerful one. Many people have wondered whether it would be possible to find a way to preserve human bodies, and what would be the best way to preserve human bodies.
    It has long been known that meat of fruit can be kept fresh for long periods by freezing: in ancient China, for example, food was stored with ice to keep it fresh. This method could also be useful for preserving humans, and in fact many people have explored this possibility.
    However, most living beings that exist under warm conditions die when frozen. This is because of the harmful effects of freezing ice crystals(晶体), which are not only larger than the volume of the water originally in the cells, but also form sharp cutting shapes that harms the cells.
    In the 1940s Dr B. J. Luyet and a group of scientists in England were working on the problem of freezing cells without damaging them. Since the harm caused by ice crystals was the main cause of the damage, Luyet suggested removing some or all of the water from the cells before freezing them.
    Using living cells from chicken, Luyet and his assistants discovered that they could partly dry the chicken cells, using a mixture of the white part of an egg and glycerin(丙三醇), a clear, thick liquid made chiefly from fats and oils. Some success was obtained. The chicken cells were dried, frozen for a period of time, and then carefully unfrozen. Almost all the cells recovered when they reached normal temperatures.
    Since then, the cooling of whole animals to a temperature very much below freezing point for later unfreezing has become more of a possibility, and the glycerin method would probably be used to accomplish this. When this can be done completely and successfully, science will have moved much closer to its aim of freezing and storing incurable patients until the day they can be cured.
Glycerin can be used______.
选项 A、to freeze living cells
B、to unfreeze living cells
C、to remove water from living cells
D、to change the shapes of crystals
答案C
解析 本题为细节题。根据定位句，冷冻前要进行脱水。鸡细胞在使用glycerin(甘油)之后，变干，然后被冷冻。由此可知glycerin(甘油)的作用是脱水。故选C。
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