What surprised Margie most about the old kind of school?

Correct answer: Children studied together in one building

Margie lives in a future where a mechanical teacher teaches one child at home, so the idea of a common school seems strange to her. The old book describes children going to a school building, sitting together, and learning from a human teacher. Margie is especially surprised that pupils of a similar age studied together in the same place instead of receiving separate lessons at home. Therefore option B is correct. Option A invents travel between planets, while C and D contradict the description of the old school: the children attended during the day and still had lessons and tests. The surprise highlights the story’s contrast between communal schooling and isolated technological instruction.