卫生类B级：阅读理解Population Densities
The average population density of the world is 47 persons per square mile. Continental densities range from no permanent inhabitants in Antarctica to 211 per square mile in Europe. In the western hemisphere， population densities range from about 4 per square mile in Canada to 675 per square mile in Puerto Rico. In Europe the range is from 4 per square mile in Iceland to 831 per square mile in the Netherlands.
Within countries there are wide variations of population densities. For example， in Egypt， the average is 55 persons per square mile， but 1，300 person inhabit each square mile in settled portions where the land is arable.职称英语
High population densities generally occur in regions of developed industrialization， such as the Netherlands， Belgium， and Great Britain， or where lands are intensively used for agriculture， as in Puerto Rico and Java. Low average population densities are characteristic of most underdeveloped countries.
Low density of population is generally associated with a relatively low percentage of cultivated land. This generally results from poor quality lands. It may also be due to natural obstacles to cultivation， such as deserts， mountains， or malaria-infested jungles; to land uses other than cultivation， as pasture and forested land; to primitive methods that limit cultivation; to social obstacles.
More economically advanced countries of low population density have， as a rule， large proportions of their populations living in urban areas. Their rural population densities are usually very low. Poorly developed countries of correspondingly low population density， on the other hand， often have a concentration of rural population living on arable land， which is as great as the rural concentration found in the most densely populated industrial countries.
36. Along the banks of the Nile， we may expect to find _______.
A. 1300 persons per square mile
B. few inhabitants
C. no inhabitant
D. few settlements
37. The most densely populated continent is ________.
A. Asia
B. Africa
C. Europe
D. North America
38. There are no permanent inhabitants in Antarctica because ________.
A. it is too hot
B. it is too cold
C. there is no transportation
D. it has only recently been discovered
39. Puerto Rico is a land of ________.
A. heavy industrialization
B. poverty
C. intense agriculture
D. large cities
40. Advanced countries of low population density may well have ________.
A. epidemics
B. arable land
C. large rural population
D. large urban population