Parallel reasoning. First strip the topic away and capture the bare logical skeleton of the analyst's argument, then find the choice whose skeleton is identical.
the analyst's skeleton has three moves: (1) two things (the Vance and Orla lines) differ on an outcome (unit sales); (2) the two things share one candidate factor (the identical television campaign); (3) because a factor the two things have in common cannot account for a difference between them, that shared factor is ruled out, and the cause is redirected to whatever the two things differ on. the load-bearing logical idea is: a shared property cannot explain a difference, so eliminate it and look among the non-shared properties.
choice (B) reproduces all three moves exactly. two offices differ on retention; they share the flexible-hours policy; the shared policy is therefore dismissed and the cause is redirected to "some respect in which the offices differ." same eliminate-the-shared-factor structure, different topic. that is the match.
Why each wrong choice is a tempting near-miss:
(A) reverses the central move. it uses a factor on which the two factories differ (the newer inspection system) and affirms it as the cause. the original eliminates a shared factor; it never affirms a differing one. affirm-the-difference is the mirror image of eliminate-the-shared.
(C) is the closest trap because it copies the original's exact wording: a shared factor "does not explain" the gap, and the cause "lies in" something else. but it redirects to a second factor the departments also share (the scheduling software). redirecting to another common factor is just as invalid as the factor it discarded, so the structure breaks at the redirect even though the sentence sounds parallel.
(D) keeps the shared factor but draws a different conclusion: that the shared drug explains the recovery rate each clinic reaches. that explains a similarity, or a level, not the difference between the clinics. a shared factor can speak to what two units have in common, never to how they differ, so the conclusion type is wrong.
(E) again affirms a differing factor (rainfall) as the cause, dressing it up with a known mechanism. the mechanism makes it feel like solid reasoning, but the original argument eliminates rather than affirms, so the shape is opposite.
the discriminating question on the whole set is simple: does the choice eliminate a factor the two things share and then point to their differences (only (B)), or does it instead affirm a cause, or redirect to another shared factor? only (B) performs the elimination-and-redirect-to-differences move that defines the original.