Sugar is so much a part of our modem 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 it 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 sugarcane ( 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 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 bas
A. What Sugar Is
B. Sugar Through the Ages
C. The Advantages of Sugar
D. Present and Future Uses of Sugar
In July 1994 Jupiter, the largest planet in our solar system, was struck by 21 pieces of a comet (慧星). When the fragments (碎片) landed in the southern part of the giant planet, the explosions were watched by scientists here on earth. But what if our own planet was hit by a comet
The year is 2094. It has been announced that a comet is heading towards the Earth. Most of it will miss our planet, but two fragments will probably hit the southern part of the Earth. The news has caused panic.
On 17 July, a fragment four kilometers wide enters the Earth’s atmosphere with a huge explosion. About half of the fragment is destroyed. But the major part survives and hits the South Atlantic at 200 times the speed of sound. The sea boils and an enormous wave is created and spreads. The wall of water rushes towards southern Africa at 800 kilometres an hour. Cities On the African coast are totally destroyed and millions of people are drowned. The wave moves into the Indian Oce
A. Because they Could only live in the warm climate.
B. Because they once dominated the earth.
C. Because their extinction indicates future disasters.
D. Because dinosaurs and humans never live in the same age.
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