填空题

One major obstacle to economic development is population
growth. The populations of most developing countries grew 21
at a rate much faster than that of industrialized countries. 22
One reason for this growth is the high crude birth-rate—the
number of alive births per 1,000 people. In some developing 23
countries, the population is so large that it is barely enough 24
futile land and other resources to support it. Many less 25
developed countries depend extensively on agriculture, adding
to the problem. In these countries, an incentive to having 26
many children exists. Most farms are worked by families,
and children can work in the fields at an early age. More
children mean more workers. In addition, having many children 27
ensures the parents that someone will look after them
in their old age. Another problem for developing countries is
increasing life expectancy—the average remaining lifetime
for persons who reach a certain age. Better education, international
aid, and emphasis on health-care facilities help people
live longer. A high life expectancy coupled with a high
crude birthrate make it difficult to increase per capita GNP. 28
Finally, people have different views on what is the proper
rate of population growth. Some feel that the earth is too
crowded already and societies should work for zero population 29
growth—the condition in which the average number of
births and deaths balances so that a population stops growing. 30
Others feel that population growth is a natural event and
that efforts to disrupt it are morally and religiously wrong.