Elite southerners maintained their power over the yeoman majority by

convincing yeomen of their shared interests.

Explanation:

Yeomen was the people who are considered to be 'middle class', they are not particularly poor but they do not have as much influence as the elite has.

By convincing the yeomen that they shared interests, the elite class can easily influence the middle class into doing something that benefit them by creating the narration that it is the best course of action for all class in society. Most of the yeomen did not even realized that they are only used as puppets by the elites.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations. click to let others know, how is it

i would say b. research typically uses a variety of sources