What was the reason for growth in the cities in the late 1800s

This was due to the expansion of industries in the U.S.. Cities grew by about 15 million people in about the two decades. Many people who helped account for the population growth of cities were immigrants arriving from around the world to live out their "American Dream". A steady stream of people from rural America also migrated to the cities during this period. Between 1880 and 1890, almost 40% of the townships in the U.S lost population due to migration. Industrial expansion and population growth changed everything. Noise, traffic jams, slums, air pollution, and sanitation and health problems were everywhere. Transit, in the form of trolleys, cable cars, and subways, were built, and even skyscrapers began to dominate cities. Communities, known as suburbs, began to be built just beyond the city. Commuters, those who lived in the suburbs and traveled in and out of the city for work, began to increase in number. New York was the most changed during this time period and became know as the "melting pot" of the world. 

With each mew y value it’s multiplied by 49. 49•49= 2401 2401•49= 117649so a. is your best bet