U2R1 P1:Urbanization is the physical growth of urban areas as a result of rural migration and even suburban concentration into cities, particularly the very large ones.由于乡村到城市的人口迁移，以及郊区人口集中涌入，特别是超大城市的郊区，导致城市人口的实际增长。This kind of growth is especially commonplace in developing countries.这种增长在发展中国家尤其普遍。____________________ (由于农村到城市的迁移), growth of urban areas ____________________(在发展中国家司空见惯).