Passage 1
A growing world's population and the discoveries of science may alter this pattern of distribution in the future. As men slowly learn to master disease, control floods, prevent famines and stop wars, fewer people die every year; and in consequence the population of the world is steadily increasing. In 1925 there were about 2000 million people in the world; by the end of the century there may well be over 4000 million.
When numbers rise, the extra mouths must be fed. New lands must be brought under cultivation, or land already farmed made to yield larger crops. In some areas the accessible land is largely so intensively cultivated that it will be difficult to make it provide more food. In some areas the population is so dense that the land is parceled out in units too tiny to allow for much improvement in farming methods. Were a large part of this farming population drawn off into industrial occupation, the land might be farmed much more productively by modern methods.
There is now a race for science, technology, and industry to keep the output of food rising faster than the number of people to be fed. New strains of crops are being developed which will thrive in unfavorable climates; there are now farms beyond the Arctic Circle in Siberia and North America; irrigation and dry-farming methods bring arid lands under the plough, dams hold back the waters of great rivers to ensure water for the fields in all seasons and to provide electric power for new industries; industrial chemistry provides fertilizers to suit particular soils; airplanes spray crops to destroy locusts and many plant diseases. Every year some new means is devised to increase or to protect the food of the world.
The author says that the world's population is growing because ________.
第一段中“in consequence the population of the world is steadily increasing”前即是原因，“fewer people die every year”，也就是人们活得越来越久了。
We are told that there are now farms beyond the Arctic Circle. This has been made possible by ________.
最后一段提到“New strains of crops are being developed which will thrive in unfavorable climates”，因此北极圈内也有了农场。
If a large part of farming population are employed in industry, the land may be cultivated ________.
由第二段最后一句“Were a large part of this farming population… the land might be farmed much more productively by modern methods”可知，如果一大部分农业人口转而从事工业，土地将会被更好地耕种。
Which of these words is nearest in meaning to the word “strain”?
由最后一段中“New strains of crops are being developed which will thrive in unfavorable climates”可知，strain表示作物的品种、类型。
This passage focuses on ________.
本文在第一段通过介绍日益增长的人口问题引出了粮食问题，第二段和第三段都讨论了粮食问题，由此可见作者的重点是粮食生产。