(A) cannot be correct. The conservative never says that socialism is inevitable, so we don't know his opinion. The socialist disagrees. So we have an unknown opinion and a disagree.
(B) is incorrect. The socialist agrees, but we have no evidence regarding the conservative's opinion on this issue.
(C) is incorrect. The conservative would disagree, but the socialist would not agree -- the socialist does not even agree that such arguments exist, so the question of whether those arguments are "justified" is a non-issue
(D) cannot be correct. The conservative says that "history occurs through accident, contingency, and individual struggle." The last part there indicates the conservative would agree with this answer. The socialist also thinks that socialists can change the world, so the socialist would agree with this answer as well. So both agree, and this cannot be the Point at Issue.
(E) is the CORRECT ANSWER. Here is what the two disagree about. The conservative claims that socialists analyze history in order to find an inevitable trend toward socialism; the socialist counters that if socialists believed history were inevitable, they wouldn't try to change anything, so they obviously think their actions have an effect and history is not inevitable. So the socialist reason for analyzing history is NOT its inevitability. Phrased more simply, the conservative says "This is why you analyze history" and the socialist says "We do analyze history, but for a different reason." So their disagreement is about why socialists do a certain thing, analyzing history. The disagreement is NOT about whether history is inevitable.
FINAL ANSWER IS (E)