(A) is incorrect because Gaby never expresses his opinion on the way schoolchildren best acquire fundamental knowledge, only Logan does. Gaby might as well agree that fundamental knowledge is best acquired through disciplined instruction, but he thinks that fundamental knowledge is unnecessary.
(B) is correct because of Gaby and Logan advocate for distinct teaching styles - "minimal guidance" versus "disciplined, systematic instruction" - that represent the opposite sides of the spectrum in terms of teacher involvement/ directing the education.