The advantages and disadvantages of a large population have long been a subject of discussion 1______ economists. 2______ has been argued that the supply of good land is limited. To feed a large population 3______ land must be cultivated and the good land worked intensively. Thus, each person produces 4______ and this means a lower average income that could be obtained with a smaller population. Other economists have argued that a large population gives more 5______ for specialization and the development of facilities such as ports, roads and railways, which are not 6______ to be built 7______ there is a big demand to justify them.
One of the difficulties in 8______ a world-wide birth control program 9______ the fact that official attitudes to population growth 10______ from country to country 11______ the level of industrial development and the availability of food and raw materials. In the developing country 12______ a vastly expanded population is pressing hard 13______ the limits of food, space and natural resources, it will be the first concern of government to place a limit ______ the birthrate, 15______ the consequences may be. In 16______ industrialized society the problem may be more complex. A decreasing birthrate may lead to unemployment because it 17______ a declining market for manufactured goods. when the 18______ of population on housing declines, prices also decline and the building industry is weakened. 19______ considerations such as these, the government of a developed country may well prefer to see a slowly increasing population, 20______ one which is stable or in decline.
7
A.if
B.unless
C.because
D.as
正确答案是B