Of all the people in the world, Asia contains ____

单项选择题

Directions: In this section, you will read several passages. Each passage is followed by several questions based on its content. You are to choose ONE best answer, (A) , (B) , (C) or (D) , to each question. Answer all the questions following each passage on the basis of what is stated or implied in that passage and write the letter of the answer you have chosen in the corresponding space in your ANSWER BOOKLET.
Questions 1～5
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 billion people in the world. It took only 75 years for the figure to double once more. 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 been increased almost everywhere and people are growing more and more food. 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. 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 countries, 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 diseases. However, all countries do not benefit to same degree from this progress in medicine and hygiene.
Half the world’s people live in Asia, but most of them are concentrated in the coastal regions and on the islands. The same type of populace concentration is true of other continents, although they are often far less populated. There are still vast regions of the world where very few people live: the central regions of the larger continents, mountainous areas, deserts, the far north, and tropical jungles.
During the nineteenth and twentieth centuries, migrations have taken place within certain countries: the cities with their industries have attracted people away from the country. The possibility of earning a fixed salary in a factory or office was more attractive than the possibility of staying on the farm and having one’s work destroyed by frost, storms, or droughts. Furthermore, the development of agricultural machinery made it possible for fewer people to do the same amount of work.
Thus, at the same time that the industrial revolution made it possible to produce goods more cheaply and more quickly in factories, an agricultural revolution also took place. Instead of leaving fields empty every third year, farmers began to plant clover or some other crop that would enrich the soil. Instead of using only animal fertilizer, farmers began to use chemical fertilizers to keep the soil rich. These methods have enabled French farmers, for example, to get five times as much wheat as was obtained from the same land two centuries ago.

Of all the people in the world, Asia contains ______.

A. one-fourth
B. one-third
C. one-half
D. two-thirds