15．In 1800，only three percent of the world's population lived in cities．Only one city-Beijing-had a population of over a million．Most people lived in rural areas，and never saw a city in their lives．In 1900，just a hundred years later，roughly 150million people lived in cities，and the world's ten largest cities all had populations exceeding one million．By 2000，the number of city dwellers exceeded three billion； and in 2008，the world's population crossed a tipping point-more than half of the people on Earth lived in cities．By 2050，that could increase to over two-thirds．Clearly，humans have become an urban species．
In the 19th and early 20th centuries，many people viewed cities negatively-crowded，dirty environments full of disease and crime．They feared that as cities got bigger，living conditions would worsen．In recent decades，however，attitudes have changed．Many experts now think urbanization （城市化） is good news，offering solutions to the problems of Earth's growing population．
Harvard economist Edward Glaeser，author of The Victory of the Cir，is one such person．Glaeser argues that cities are very productive because"the absence of space between people"reduces the cost of transporting goods，people，and ideas．While the flow of goods has always been important to cities，what is most important today is the flow of ideas．Successful cities enable people to learn from each other easily，and attract and reward smart people with higher wages．
Another urbanization supporter is environmentalist Stewart Brand．Brand believes cities help the environment because they allow haft of the world's population to live on about four percent of the land．This leaves more space for open country，such as farmland．City dwellers also have less impact per person on the environment than people in the countryside．Their roads，sewers，and power lines need fewer resources to build and operate．City apartments require less energy to heat，cool，and light．Most importantly，people in cities drive less so they produce fewer greenhouse gases per person．
So it's a mistake to see urbanization as evil； it's a natural part of development．The challenge is how to manage the growth．
4．What is Paragraph 1mainly about？C
A．The history of modern cities．
B．Changes taking place within cities．
C．How cities have grown over time．
D．Why modern cities are changing．
5．How have experts'attitudes towards cities changed in recent decades？A
A．They now view the weaknesses as strengths．
B．They no longer see city-riving as attractive．
C．They accept city life in spite of its problems．
D．They think city-riving provides more benefits．
6．Which of the following would Edward Glaeser agree with？B
A．Cities provide more economic opportunities．
B．City people get along better with each other．
C．Over-crowded cities result in problems．
D．Cities limit the flow of ideas．
7．According to Paragraph 4，what would be the result of moving people out of cities？D
A．Economic production would be reduced．
B．There would be less farmland available．
C．People would travel less frequently．
D．House values would fall greatly．
分析 本文属于说明文阅读，作者通过这篇文章向我们介绍了城市中的人口是如何随着时间而增长的，以及城市化的好处以及劣势．
解答 4．C 推理判断题，根据第一段in 2008，the world's population crossed a tipping point-more than half of the people on Earth lived in cities．By 2050，that could increase to over two-thirds．可知第一段主要向我们介绍了城市中的人口是如何随着时间而增长的，故选C．
5．A 细节理解题，根据第二段In the 19th and early 20th centuries，many people viewed cities negatively-crowded，dirty environments full of disease and crime．以及Many experts now think urbanization （城市化） is good news，offering solutions to the problems of Earth's growing population可知在十九世纪和二十世纪初，许多人认为城市拥挤肮脏的环境中充满了消极，疾病和犯罪，而现在专家们认为城市化是个好消息，故选A．
6．B 细节理解题，根据第三段Successful cities enable people to learn from each other easily，and attract and reward smart people with higher wages．可知Edward Glaeser 认为城市化中的人与人之间相处的更好，故选B．
7．D 细节理解题，根据第四段City dwellers also have less impact per person on the environment than people in the countryside．Their roads，sewers，and power lines need fewer resources to build and operate．City apartments require less energy to heat，cool，and light可知如果人们搬离城市，那么城市中的房价将大幅下跌，故选D．
点评 考查学生的细节理解和推理判断能力．做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确选择．在做推理判断题时不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
