Why does the old school become almost like a dream for Margie?

Correct answer: Because she never experienced such a social school

The governing concept is contrast created by lack of experience. Margie has always studied alone at home with a mechanical teacher, so the description of an old school filled with children, human interaction and a shared timetable is completely unfamiliar to her. Because she has never lived that experience, it seems wonderful, distant and almost unreal, like a dream. Option A is correct. She has seen a machine, so B is factually unsuitable; she does study, so C misrepresents her attitude; and Tommy only discovers and explains the book, so D confuses his role with the creation of a school.