Sugar is so much a part of our modern life that we only really think about it when,for some reason,we cannot obtain it. (1)_________________,but has come into common use only in modern times. Until quite recently it was considered as a medicine and as a luxury for the very rich only. Sugar is,then,very important to our civilization. But what exactly is it? (2)__________________which we put in coffee or cakes. This common form of sugar is derived from two plants;the sugar cane and the sugar beet. But there are in fact many types of sugar,and the chemist recognises hundreds of different varieties,each coming from a different source. (3)____________________. Only 10% is used in industry for purposes other than food production. Yet sugar has great possibilities for use as the basis of chemicals. It can even be used for making plastics. In the future these potential uses will certainly be developed more than in the past.
发表于 2011-5-13 13:21
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发表于 2011-5-16 21:27
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