On what basis was the mechanical teacher's lesson adjusted?

Correct answer: On Margie's level

The governing idea is personalised, technology-based education. In Isaac Asimov’s story, Margie’s mechanical teacher did not give exactly the same lesson to every child; its Geography sector was adjusted to suit Margie’s level. This means the machine could respond to her learning needs and modify the difficulty or pace of instruction. Therefore, option A is correct. Tommy’s book only introduces Margie to the old style of schooling, while weather and the size of the attic have no connection with the lesson. The episode shows both the convenience and the limitation of automated teaching: it can be adjusted, but it still requires human inspection when it malfunctions.