To understand the most important characteristics of a society, one must study its major cities. [Specific Task Instruction: Write a response in which you discuss the extent to which you agree or disagree with the statement and explain your reasoning for the position you take. In developing and supporting your position, you should consider ways in which the statement might or might not hold true and explain how these considerations shape your position.]
The author suggests that a researcher must study the major cities of a society in order to understand its most important characteristics. Basically I agree with this point 
Undoubtedly the major cities stand for a civilization, serving as its window, and concentrating its important characteristics. For a society, a major city is its center of economy, culture, and politics--all of which are among the most crucial characteristics of this society. To understand the Empire of Rome, we can but begin from its center and capital, the city of Rome. To do research on United States, we are unable to avoid the study of New York, Washington, and Los Angels. Some opponents may state that there are still some societies whose essence resides not in cities but rural areas, for example, some Native American culture, or some ancient societies on Pacific islands. But, however, this is because no "major city" is available for them. Even there are some "major site" for these people, which is, actually, the "major cities" for these relatively underdeveloped civilizations. Accordingly, we must study the major cities of a society, if we want to better understand it, unless there is not any.
Also, we have to admit that major cities are not only built but also developed. Usually a major city has its own history, a history about establishment, prosperity, declination, even devastation. Many people, and social and cultural products are involved. Such a history will have a lot to do with the characteristics of the society which owns the major city. For example, as the capital of China for centuries, Beijing is a city more than meets the eyes. In its history and products, we can find traces about the development and evolution of Chinese society, especially those about politics issues. Shanghai and Guangzhou, another two major cities of China, reflects more about economic and regional cultural issues. A research on characteristics of "Chinese society" can hardly be convincing if the researcher doesn't pay attention on these cities. Again, the opponents may cite some studies on some Chinese rural area or village, arguing that the characteristics of a society are "not limited to major cities". However, since in present days near half of Chinese are populated in cities, a research on a village may not reflect anything about "Chinese society" if it is not associated with some Chinese cities. And the association with major cities could be the most representative way. 
Accordingly, I agree with the author's point, that study on major cities is necessary for almost all researchers, if they want to understand the characteristics of a society, and if this society has any major city.