Questions 16 to 20 are based on the following passage:

　　The advantages and disadvantages of large population have long been a subject of discussion among economists. It has been argued that the supply of good land is limited. To feed a large population, inferior land must be cultivated and the good land worked intensively. Thus, each person produces less and this means a lower average income than could be obtained with a smaller population. Other economists have argued that a large population gives more scope for specialization and the development of facilities such as ports, roads and railways, which are not likely to be built unless there is a big demand to justify them.

　　One of the difficulties in carrying out a world- wide birth control program lies in the fact that official attitudes to population growth vary from country to country depending on the level of industrial development and the availability(获得的可能性)of food and raw materials. In the developing countries where a vastly expanded population is pressing hard upon the limits of food, space and natural resources, it will be the first concern of government to place a limit on the birthrate, whatever the consequences may be. In a highly industrialized society the problem may be more complex. A decreasing birthrate may lead to unemployment because it results in a declining market for manufactured goods. When the pressure of population on housing declines, prices also decline and the building industry is weakened. Faced with considerations such as these, the government of a developed country may well prefer to see a slowly increasing population, rather than one which is stable or in decline.

　　16. According to the passage, slowly rising birthrate perhaps is good for _____.

　　A. a developed nation

　　B. a developing nation

　　C. every nation with a small population

　　D. every nation with a big population

　　17. A small population may mean _________.

　　A. higher productivity and a higher average income.

　　B. Lower productivity and a lower average income

　　C. Higher productivity, but a lower average income

　　D. Lower productivity, but a higher average income

　　18. In a developed country, people will perhaps go out of work if the birthrate

　　__________.

　　A. is out of control B. goes down

　　C. goes up D. remains stable

　　19. It is no easy job to carry out a general plan for birth control throughout the

　　world because ______.

　　A. even developed countries may have complex problems

　　B. there are too many underdeveloped countries in the world

　　C. different governments have different views of the question

　　D. underdeveloped countries have low level of industrial development

　　20. According to the passage, a large population will provide a chance fordeveloping __________.

　　A. industry B. national economy

　　C. agriculture D. transport system