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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  65
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一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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