Answer: The right answer is the C) The isolated lower classes.
Explanation: Just to elaborate a little on the answer, it can be added that the only thing that we can infer from these lines is that these two female characters lived in isolation, since, when the mother saw a stranger coming up their road, she looked in the direction he was coming from, and this suggests that she was not accustomed to see people around. Later on in the story (Flannery O'Connor's “The Life You Save May Be Your Own”) the reader will discover that the daughter has indeed a disability, but this cannot totally be discerned from these initial lines - although the fact that the girl did not look in the direction of the stranger does suggest that she could not hear him approaching, since a child in that circumstance would have reacted at least with curiosity.