[阅读理解]

【题干】About three hundred years ago, there were approximately half a billion people
in the world. In the two centuries that followed the population doubled, and, by
1850, there were more than a bllion people in the world. It took only 75 years for
the figure to double once more, so that now the population figure stands at
approximately six and one half bllion. Each day the population of the world
increases by about 150,000.
In former centuries the population grew slowly. Famines, wars, and epidemics,
such as the plague and cholera, killed many people. Today, although the birth rate
has not changed significantly, the death rate has been lowered considerably by
various kinds of progress.
Machinery has made it possible to produce more and more food in vast areas,
such as the plains of America and Russia. Crops have increased almost everywhere
and people are growing more and more food. New forms of food preservation have
also been developed so that food need not be eaten as soon as it has grown. Meat,
fish, fruit and vegetables can be dried, tinned or frozen, then stored for later use.
Improvement in communications and transportation has made it possible to
send more food from the place where it is produced to other places where it is
needed. This has helped reduce the number of famines.
Generally speaking, people live in conditions of greater security. Practices such
as the slave trade, which caused many uscless deaths, have been stopped.
Progress in medicine and hygiene has made it possible for people to live longer.
People in Europe and North America live, on the average, twice as long as they did
a hundred years ago. In other counties, too, people generally live much longer than
they once did. Babies, especially, have a far better chance of growing up because of
increased protection against infant disease. However, all countries do not benefit to
the same degree from this program in medicine and hygiene.

【题目】【概括词汇】27. a particular amount expressed as a number (Para. 1)

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