Sugar is so much a part of our modern life that we only 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 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 from two plants: the sugar cane (a type of grass which grows to a height of 20 feet) and the sugar beet (which grows underground). But in fact there are many types of sugar, and the chemist recognizes 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. There are many reasons why we should increase the production of sugar. Most important is that it is one of the most highly concentrated energy foods. Thus sugar cane and beet produce an average of 7,000,000 calories per acre. In this way they have the advantages over potatoes which give only 4,000,000, while the figure for wheat and beans is 2,000,000 each. So three acres of land growing wheat, beans and potatoes give only slightly more energy than one acre of sugar.
1．The heading of Paragraph One may be ______.
A．What Sugar Is B．Sugar Through Ages
C．The Advantages of Sugar D．Present And Future Uses of Sugar
2．The third paragraph emphasizes (强调) ______.
A．about 90% of sugar is used as food B．only 10% is used in industry
C．sugar used for making plastics D．future uses of sugar
3．Sugar has been used widely ______.
A．for 3,000 years B．in modern times
C．until quite recently D．for 300 years
4．The main reason why we should increase the production of sugar is that ______.
A．sugar tastes sweet B．we can save plenty of land
C．we can take in more energy D．it provides much energy