It is generally agreed that the first true cities appeared about 5,000 years ago in the food-producing communities of the Middle East. The cities of Sumeria,Egyptand the Indus Valley possessed a number of characteristics that distinguished them as truly urban. The cities were very much larger 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（亲属关系）relations were replaced by a complex hierarchy（等级）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（复杂程度）of urban society gave a new impetus（推动力）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 ofGreeceand Rome. We can trace three main phases（阶段） in the growth of the West European city. The first of these is the medieval phase, which extends from the beginning of the 11th A. D. to about 1,500. The second is the renaissance（文艺复兴） and Baroque phase, which can be traced from 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（焦点）. This would be a permanent structure such as a stronghold（要塞）, 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 routs met. In studies of urban geography the oldest part of town is referred to as the nuclear settlement. There are many small towns in Europe where it is still possible to trace（追踪）the outline of the original（原先的） 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.Which of the following statements is TRUE?