It has been known to man for at least 3,000 years,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?
Of course most of us recognize sugar immediataly as the sweet material 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.
About 90% of the sugar is produced as food.
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.
Questions 11 to 13 are based on the passage you have just heard.
11.How long has sugar been used widely?
12.What material is mentioned that can be made from sugar?
13.Which of the following statements is true?
为了帮助大家更好的突破四六级听力考试,根据历年命题特点和命题趋势,整理了以下预测试题:
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