The advantages and disadvantages of a large population have long

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.
11
A、to depend on
B、depend on
C、depending on
D、depended on
【正确答案】：C
【题目解析】：分析句子可知本句已经有谓语“vary”，故本空只能选非谓语形式。A.to depend on动词不定式表示目的，不符合本句句意。本句主语和depend非被动关系，故D不对。因此选C,-ing分词做状语。答案为C。