What difference appears when Margie's schoolroom is compared with the old school building?

Correct answer: Private loneliness and public togetherness

The governing contrast is between isolated home-based instruction and a shared school community. Margie’s schoolroom is a room in her house where she studies alone with a mechanical teacher. The old school building, as she imagines it from Tommy’s description, brought many children together in one place and included a human teacher. Thus option A is correct: Margie experiences private loneliness, whereas the old school represented public togetherness. The two settings are not identical, neither is described merely as a place for play, and the old building was associated with human teaching rather than being full of machines. This contrast supports the story’s concern with social learning.