A. They feared competition with a formerly enslaved population over land and social status.
Explanation:
Poor whites and rich whites had one thing in common- their race. The fact that despite their social status, they all belonged to the same race, and they shared the ideology of white supremacy, made the poor whites support the institution of slavery so that the blacks could remain below them. They also feared that black slaves could gain their voice and power and begin competing with them for their lands and social status.
The poor whites who did not own slaves ensured that black slaves did not escape from their masters. They also participated in other civil duties in the society such as voting.
