[单项选择] 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. 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 immediately as the sweet material which we put in coffee or cakes. This common form of sugar is derived from two plants: the sugar cane (a type of grass which grows to a height of twenty feet) and the sugar beet (which grows underground). But there are in fact many types of sugar, and the chemist recognizes hundreds of different varieties, each coming from a different source. About 90% of the sugar 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 chemica
A. it tastes sweet
B. we can save plenty of land
C. we can get more energy
D. it is one of the most highly concentrated of energy food