题目内容：
根据下面材料，回答题。It is generally agreed that the first true cities appeared about 5,000 years ago in the food-produ-cing communities of the Middle East．The cities of Sumeria, Egypt and the Indus Valley possessed a number of characteristics that distinguished them as truly urban．The cities were very much large and more densely populated than any previous settlement, and their function was clearly differentiated from that of the surrounding villages．In the cities the old patterns of kinship relations were replaced by a complex hierarchy of social classes based on the specialization of labor．Moreover, the need to keep records led to the development of writing and arithmetic, and the increased sophistication of ur-ban society gave a new impetus to artistic expression of every kind．
When the basis of city life was established in Europe, the urban tradition was drawn from the ancient cities of the Middle East, via the civilization of Greece and Rome．We can trace three main phases in the growth of the West European city．The first of these is the medieval phase,which extends from the beginning of the 1 lth century A, D．to about 1,500 to the beginning of the 19th century．The third is the modern phase extending from the early 19th century to the present day．
Every medieval city began as a small settlement, which grew up round a geographical or cultural focal point．This would be a permanent structure such as a stronghold, a cathedral or a large church．
In districts where travel and trade were well established, it might be a market, a river crossing, or a place where two or more trade routes met, in studies of urban geography the oldest part of town is re-ferred to as the nuclear settlement．There are many small town in Europe where it is still possible to trace the outline of the original nuclear settlement．It is, of course, much more difficult to do this in the case of a large modern city which has grown to many times its original size．
The ancient cities were characterized by all the following except__________． A．larger populations
B．different roles
C．different social classes
D．different locations
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