What did Margie feel while thinking about old schools?

Correct answer: Children must have had fun

The governing idea is the story’s contrast between mechanical isolation and the lively social experience of old schools. After reading about children learning together in a school building, Margie imagines that they must have enjoyed themselves. Thus, option A is correct and connects directly with the title, The Fun They Had. Option B is unsupported because the story does not present old school life as constant sorrow. Option C contradicts the presence of groups of children, and option D reverses the important distinction between old human teachers and future machines. Her thought shows curiosity and a growing appreciation of shared education.