Matching the influx of foreign immigrants into the larger cities of the United States during the late nineteenth century was a domestic migration, from town and farm to city, within the United States. The proportion of urban population began to grow remarkably after 1840, increasing from 11 percent that year to 28 percent by 1880 and to 46 percent by 1900. A country with only 6 cities boasting a population of more than 8,000 in 1800 had become one with 545 such cities in 1900. Much of the migration producing an urban society came from smaller towns within the United States, but the combination of new immigrants and old American "settlers" on America’’s "urban frontier" in the late nineteenth century proved extraordinary. The growth of cities and the process of industrialization fed on each other. The agricultural revolution stimulated many people in the countryside to seek a new life in the city and made it possible for fewer farmers to feed the large concentrations of people needed to provide a workforce for growing numbers of factories. Cities also provided ready and convenient markets for the products of industry, and huge contracts in transportation and construction—as well as the expanded market in consumer goods—allowed continued growth of the urban sector of the overall economy of the United States. Technological developments further stimulated the process of urbanization. One example is the Bessemer converter(an industrial process of manufacturing steel), which provided steel girders for the construction of skyscrapers. The refining of crude oil into kerosene, and later the development of electric lighting as well as of the telephone, brought additional comforts to urban areas that well unavailable to rural Americans and helped attract many of them from the farms into the cities. In every era the lure of the city included a major psychological element for country people; the bustle and social interaction of urban life seemed particularly intriguing to those raised in rural isolation. What contribute to the growing number of domestic migration

A. Industrialization.
B. Technological development.
C. lack of farming land.
D. Both A and B.