By the mid-1800s, most enslaved people in the American south A. Worked as domestic servants
B. Lived on large plantations

Honestly they are both correct. They did live on large agricultural plantations as horse servants or field hands. They also were house servants. Most enslaves women worked as domestic servants and most enslaved men worked on the plantation. But; looking at this question they are mainly asking where enslaved people in the American south lived not what they did. So the answer would be, B- Lived on large plantations.

Explanation:

In the early 19th century, most enslaved men and women worked on large agricultural plantations, as house servants, or field hands. Life for the  enslaved  was brutal; they were subject to repression, harsh punishments, and strict racial policing.

the reform movements that arose during the antebellum period in america focused on specific issues: temperance, abolishing imprisonment for debt, pacifism, antislavery, abolishing capital punishment, amelioration of prison conditions (with prison's purpose reconceived as rehabilitation rather than punishment), the humane treatment of animals, the humane and just treatment of native americans, the establishment of public institutions for the care of the destitute, orphans, blind, and mentally ill, the establishment of public schools, the abolition of tobacco use, vegetarianism, health reform, homeopathic medicine, woman's rights (including, at first, especially the establishment of a woman's right to own property apart from her husband and her right to sue for divorce), and the amelioration of labor conditions (including higher pay, the right to form unions, the right to strike, and the demand for limits on the number of work hours, and safe working conditions).

explanation: