@kyoon the principle here is that one can enhance their understanding of a certain period by studying earlier periods that had a significant influence on it.
Notice that (B) does not conform to this principle.
(B) states, "To understand fully the historical events of this century, a historian must have an understanding of similar events in earlier centuries."
There is nothing in (B) that indicates these similar events in earlier centuries had a significant influence on the historical events of this century. This is why (B) is incorrect.
Compare that with (E), "To understand completely Aristotle's philosophy, one must be well acquainted with the philosophy of his intellectual mentor, Plato."
Notice that not only is Plato from an earlier period, but he also had a significant influence on Aristotle because he was Aristotle's mentor.
Hope that helps! Please let us know if you have any other questions.
