This is a classic GMAT Critical Reasoning question that tests your ability to identify the Structure of the Argument (Method of Reasoning).
The correct answer is (B). Let's break down the logic of the passage and analyze why this option fits perfectly while the others fall short.
Breaking Down the Logic
The Historian's Argument:
* Premise: There are massive linguistic similarities between King Alfred's known translations and his law code.
* Historian's Conclusion: Therefore, King Alfred must have personally written the law code.
* The Historian's Underlying Assumption: If two texts from this period share deep linguistic similarities, it must mean they share the same author (common authorship).
The Author's Counter-Argument:
* The Counter-Fact: Linguistic similarities are completely normal for any texts written in the same language, time period, and region.
* The Problem: We only have two other surviving texts from this entire region and era to compare them to.
* Author's Conclusion: Because our sample size is so tiny, we cannot assume that similarity equals the same author. It's just how people talked back then in that specific area.
By pointing out that the similarities could just be a product of the "dialect and milieu" (the time and place) rather than a unique authorial voice, the author attacks the historian's assumption that similarity implies common authorship.
Detailed Option Analysis
(A) Providing examples that underscore another argument's conclusion.
* Incorrect. The author is trying to destroy the historian's conclusion, not support or "underscore" it.
(B) questioning the plausibility of an assumption on which another argument depends.
* Correct. As established, the historian's argument depends entirely on the unstated assumption that linguistic similarities prove common authorship. The author directly questions the plausibility of this assumption by showing that the similarities are likely just standard regional traits, made impossible to verify uniquely because we lack enough surviving texts for comparison.
(C) showing that a principle if generally applied would have anomalous consequences.
* Incorrect. The author does not take the historian's logic and apply it generally to other situations to show it creates weird or "anomalous" (abnormal) results. The author stays strictly focused on the lack of surviving evidence from King Alfred's specific era.
(D) showing that the premises of another argument are mutually inconsistent.
* Incorrect. For premises to be "mutually inconsistent," they would have to contradict each other (e.g., if the historian said "the texts are very similar" and "the texts are completely different" at the same time). The historian's premises are perfectly consistent; they are just based on a flawed assumption.
(E) using argument by analogy to undermine a principle implicit in another argument.
* Incorrect. An "argument by analogy" involves comparing the current situation to a completely different but parallel scenario (e.g., "Assuming Alfred wrote the laws because of language similarities is like assuming two modern internet blogs were written by the same person just because they both use American slang."). The author uses no such analogy here; the critique remains entirely historical and textual.
Takeaway for the GMAT: On "Method of Reasoning" questions, look for the standard logical moves. When an author argues that a piece of evidence (similarities) could be explained by a general trend (everyone spoke that way then) rather than a specific cause (the King wrote it), they are exposing a flawed assumption of uniqueness.