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  3. Thomas Malthus published his Essay on the Principle of Populationalmost 200

Thomas Malthus published his Essay on the Principle of Populationalmost 200

游客2023-10-14  47
问题     Thomas Malthus published his Essay on the Principle of Population
almost 200 years ago. Ever since then, forecasters have being warning                      【M1】________
that worldwide famine was just around the next comer. The fast-growing
population’s demand for food, they warned, would soon exceed their                        【M2】________
supply, leading to widespread food shortages and starvation.
    But in reality, the world’s total grain harvest has risen steadily over the
years. Except for relative isolated trouble spots like present-day Somalia,                【M3】________
and occasional years of poor harvests, the world’s food crisis has remained               【M4】________
just around the comer. Most experts believe this can continue even as if                   【M5】________
the population doubles by the mid-21st century, although feeding 10 billion
people will not be easy for politics, economic and environmental reasons.                  【M6】________
Optimists point to concrete examples of continued improvements in yield.
In Africa, by instance, improved seeds, more fertilizers and advanced                      【M7】________
growing practices have more than double com and wheat yields in an                         【M8】________
experiment. Elsewhere, rice experts in the Philippines are producing
a plant with few stems and more seeds. There is no guarantee that plant                    【M9】________
breeders can continue to develop new, higher-yielding crop, but most                       【M10】________
researchers see their success to date as reason for hope. [br] 【M7】
选项
答案 by→for
解析 该句的意思是“例如，在非洲，在一项试验中，改良种子、更多化肥和先进的种植方法使玉米和小麦产量增加了一倍以上”。for instance为固定用法，表示“例如”。因此将by改为for。
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