With the development of new technologies and manufacturing processes, the nature of factory work changed. Now, machines could do the heavy labor formerly done by men. This meant that women and children could work in factories. In fact, factories sometimes hired entire families. They earned hourly wages. While this could bring in a steady income, that income was not high. Women earned less than men, and children’s wages were especially low. A. identifies a central trend.
B. provides some key details.
C. makes clear the writer’s opinion.
D. states the main idea of the summary.

“With the development of new technologies and manufacturing processes, the nature of factory work changed.” Is the underlined.