单选题
The principal factor depressing life expectancy in
developing countries has always been the high death rate for infants and
children. The World Bank studies suggest that as much as two thirds of the
difference in life-spans between people in developed countries and those in
developing ones can be traced to differences in survival rates for children
under five. It is here where the most improvement has come. According to
UN estimates, significant regional drops in infant mortality - ranging from 25
percent to 60 percent and centering near 40 percent - appear to have taken place
between the late 1950s and the late 1970s in northern Africa, Latin America, and
Asia. Although sub-Saharan Africa' s mortality trends cannot be quantified with
confidence, there is reason to believe that life expectancy has risen and
infant mortality has declined in that region as well. There is little
doubt that population growth has accelerated in sub-Saharan Africa since the
1950s; in fact, sub-Saharan Africa is widely thought to have the highest rate of
population growth of any major region in the world. Only a small portion of that
acceleration is likely to have been caused by increases in fertility (and
increases in fertility, insofar as they have occurred, may also imply
improvements in health and nutrition). Mortality, of course, is
not a perfect measure of nutritional change. Improved nutrition is only one of a
number of forces that have been pushing down death rates in developing
countries. Others include the upgrading of hygiene and sanitation; the
extension of public health services; medical innovations;
improvements in education, communications, transportation, and, in some areas,
civil order. Even so, the extent to which improvements innutrition—both
direct and indirect—have reduced mortality in developing countries has
frequently been underestimated. For example, Sri Lanka experienced an
abrupt jump in life expectancy shortly after the Second World War. Whereas
this was long described as a "technical fix"—a triumph of DDT over the anopheles
mosquito—years later researchers realized that abrupt and rapid drops in
mortality had also taken place in Sri Lanka' s highlands, or "dry zones", where
malaria had never been a serious problem. In both highlands and lowland
regions health improved in tandem with access to food.
单选题
According to the author, life expectancy in developing countries is not
high mainly because developing countries______.
A. have a low standard of living
B. have no public health services
C. have no public and private hygiene and sanitation
D. have low survival rates for infants and children
【正确答案】
D
【答案解析】从第一段第二句可以看出答案。
单选题
Between the late 1950s and the late 1970s, infant mortality in northern
Africa______.
A. still remained high
B. fell sharply
C. was lower than that in Asia
D. rose tremendously
【正确答案】
B
【答案解析】从文中第四句中联合国统计的数据可以看出答案为B。
单选题
The author holds that______.
A. mortality rates in developing countries have been brought down by a
number of forces
B. medical innovations are the only way to reduce mortality rates in
developing countries
C. the upgrading of hygiene and sanitation has played a crucial role in
reducing mortality rates in developing countries
D. improved nutrition is the only one factor that reduces mortality rates in
developing countries
【正确答案】
A
【答案解析】文中第二段论述了降低死亡率的多种因素。
单选题
It can be inferred from the last paragraph that before the Second World
War,______.
A. malaria had taken few lives in Sri Lanka
B. malaria had been a very serious problem in lowland regions in Sri
Lanka
C. malaria had remained unrestrained in Sri Lanka
D. malaria had been already put under control in Sri Lanka