Historically, the spread, prevalence, and very existence of contagious disease have wholly depended on the growth and concentration of human populations.（1） And though the last century has witnessed substantial worldwide success in combating many past scourges —such as polio and smallpox — infectious diseases still claim more lives than any other group of diseases. The prevailing demographic trends continue to create a crowded human “medium” that both invites and is vulnerable to infection.
The share of humanity living in cities with more than 1 million people has surged from less than 5 percent in 1900 to nearly 40 percent today, creating the ideal setting for the resurgence of old infectious diseases as well as the development of new ones.（2）
Overcrowding — the increased proximity of susceptible individuals — is a principal risk factor for the incidence and spread of all major infectious diseases, including tuberculosis, dengue fever, malaria, and acute respiratory illnesses, which are unable to spread and survive in low population densities.（3）
Aside from sheer growth and increasing density, the urbanization under way in developing nations is often accompanied by deteriorating health indicators and increased exposure to disease risk factors.
Access to clean water, good hygiene, and adequate housing are sorely lacking in developing nations. As a result, waterborne infections such as cholera and other diarrheal diseases account for 90 percent of all infectious diseases in developing countries — and 40 percent of all deaths in some nations.（4）
In both industrial and developing nations, the incidences of a wide range of infectious diseases, including tuberculosis, diarrheal diseases, and HIV/AIDS, are considerably higher in urban slums — where poverty and compromised health define the way of life — than in the rest of the city.（5 ）
问题1选项
A.Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread.
B.The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population.
C.Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims.
D.While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow.
E.Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread.
F.These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain.
问题2选项
A.Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread.
B.The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population.
C.Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims.
D.While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow.
E.Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread.
F.These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain.
问题3选项
A.Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread.
B.The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population.
C.Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims.
D.While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow.
E.Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread.
F.These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain.
问题4选项
A.Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread.
B.The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population.
C.Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims.
D.While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow.
E.Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread.
F.These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain.
问题5选项
A.Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread.
B.The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population.
C.Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims.
D.While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow.
E.Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread.
F.These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain.
第1题:B
第2题:E
第3题:A
第4题:C
第5题:F
第1题:
【选项释义】
A. Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread. A. 昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。
B. The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population. B. 例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。
C. Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims. C. 尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。
D. While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow. D. 虽然新的全球市场创造了前所未有的经济机会和增长，但我们这个相互联系日益紧密、节奏越来越快的世界的健康风险继续增加。
E. Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread. E. 病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。
F. These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain. F. 这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。
【考查点】联系上下文
【解题思路】第一句为起始句，其后部分展开解释说明。同时我们可以发现第三句是举例解释第一句话，由此可判断第二句应该也是解释说明第一句的。选项B中的in fourteenth-century Europe与第三句中的the last century分别从两个历史时期举例解释段首。从而得出本题答案B选项“例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。”
第2题:
【选项释义】
A. Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread. A. 昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。
B. The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population. B. 例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。
C. Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims. C. 尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。
D. While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow. D. 虽然新的全球市场创造了前所未有的经济机会和增长，但我们这个相互联系日益紧密、节奏越来越快的世界的健康风险继续增加。
E. Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread. E. 病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。
F. These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain. F. 这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。
【考查点】联系上下文
【解题思路】全文只有在本段中提到了具体的人口数量，与选项E中的a critical number of vulnerable individuals（关键数量的弱势群体）在内容上互相呼应。从而得出本题答案E选项“病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。”
第3题:
【选项释义】
A. Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread. A. 昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。
B. The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population. B. 例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。
C. Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims. C. 尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。
D. While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow. D. 虽然新的全球市场创造了前所未有的经济机会和增长，但我们这个相互联系日益紧密、节奏越来越快的世界的健康风险继续增加。
E. Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread. E. 病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。
F. These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain. F. 这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。
【考查点】联系上下文
【解题思路】本段的主要内容：城市人口密度大成为传染病流行的重要原因。因此段首的overcrowding和选项A中的crowded为本段的关键词。从而得出本题答案A选项“昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。”
第4题:
【选项释义】
A. Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread. A. 昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。
B. The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population. B. 例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。
C. Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims. C. 尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。
D. While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow. D. 虽然新的全球市场创造了前所未有的经济机会和增长，但我们这个相互联系日益紧密、节奏越来越快的世界的健康风险继续增加。
E. Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread. E. 病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。
F. These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain. F. 这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。
【考查点】联系上下文
【解题思路】选项C中的water and sanitation（水和卫生设施）与本段首句中提到的clean water, good hygiene（干净的水，良好的卫生）内容一致。从而得出本题答案C选项“尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。”
第5题:
【选项释义】
A. Key disease carriers, such as insects and rats, thrive in crowded urban settings, further facilitating spread. A. 昆虫和老鼠等主要疾病携带者在拥挤的城市环境中茁壮成长，进一步促进了传播。
B. The unprecedented population densities in fourteenth-century Europe, for example, led to the plague outbreak that claimed the lives of one fourth of the population. B. 例如，14世纪欧洲前所未有的人口密度导致鼠疫爆发，夺去了四分之一人口的生命。
C. Although these infections are easily preventable if adequate water and sanitation are available, the vast majority of the world’s population are lifelong victims. C. 尽管如果有足够的水和卫生设施，这些感染很容易预防，但世界上绝大多数人口都是终生受害者。
D. While new global markets have created unprecedented economic opportunities and growth, the health risks of our increasingly interconnected and fast-paced world continue to grow. D. 虽然新的全球市场创造了前所未有的经济机会和增长，但我们这个相互联系日益紧密、节奏越来越快的世界的健康风险继续增加。
E. Pathogens can more readily establish in large populations, since all infectious diseases require a critical number of vulnerable individuals in order to take root and spread. E. 病原体更容易在大量人群中建立，因为所有传染病都需要大量脆弱的个体才能扎根和传播。
F. These areas can serve as a perpetual reservoir of disease or disease vectors, placing other parts of the city at risk of an outbreak and allowing the disease to continue evolving, often into a deadlier strain. F. 这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。
【考查点】联系上下文
【解题思路】本段的主要内容：城市贫民窟的情况。选项F中These areas与 other parts of the city分别指的就是前文所说的贫民窟和城市的其他区域。从而得出本题答案F选项“这些地区可以作为疾病或疾病媒介的永久储存库，使城市的其他地区面临爆发的风险，并使疾病继续发展，通常会演变成更致命的毒株。”
