Thomas Malthus published his "Essay on the Principle of Population" almost 200 years ago. Ever since then, forecasters have bei

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问题     Thomas Malthus published his "Essay on the
Principle of Population" almost 200 years ago. Ever
since then, forecasters have being warning that (1)______
worldwide famine was just around the next corner.
The fast-growing population’s demand for food, they
warned, would soon exceed their supply, leading to (2)______
widespread food shortages and starvation.
    But in reality, the world’s total grain harvest
has risen steadily over the years. Except relatively (3)______
isolated trouble spots like present-day Somalia, and
occasional years of good harvests, the world’s food (4)______
crisis has remained just around the corner. Most
experts believe this can continue even as if the (5)______
population doubles by the mid-21st century,
although feeding 10 billion people will not be easy
for politics, economic and environmental reasons. (6)______
Optimists point to concrete examples of continued
improvements in yield. In Africa, by instance, im- (7)______
proved seed, more fertilizer and advanced growing
practices have been more than doubled corn and wheat (8)______
yields in an experiment. Elsewhere, rice experts in
the Philippines are producing a plant with few stems (9)______
and more seeds. There is no guarantee that plant
breeders can continue to develop new, higher-yield
ing crops, and most researchers see their success to (10)______
date as reason for hope.
(10)

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