How did changes in manufacturing in the late 1700s and early 1800s affect people living in northern cities? a. fewer people worked in factories as water-powered machines increasingly replaced laborers. b. factories used interchangeable parts and water power, so workers’ hours became shorter. c. factories employed more people, including women and children, for lower wages and longer hours. d. as factory employment became less widely available, people began leaving the cities to work in agriculture.