Wrong flaw. (A) sets up a conditional relationship (if allowed to dress casually, then it’s Friday), but it brings up the new variable of Hector dressing formally. How Hector is dressed has no bearing on whether he is allowed to dress casually, so the conclusion doesn’t follow. The stimulus, meanwhile, concludes that the absence of a sufficient condition leads to the absence of a necessary condition, so (A) doesn’t match.

(B) establishes a conditional relationship: If you take the class, then you’re a music lover. It then concludes that Hillary’s failure to meet the sufficient condition (not taking the class) means that she doesn’t meet the necessary condition (she’s not a music lover). The stimulus also concludes that the absence of a sufficient condition leads to the absence of a necessary condition, so (B) matches.

No flaw. (C) establishes a conditional relationship (if you enjoy the Atlantic in midwinter, then you’re an oceanographer) and validly concludes that the absence of the necessary condition leads to the absence of the sufficient condition. The stimulus, meanwhile, concludes that the absence of a sufficient condition leads to the absence of a necessary condition, so (C) doesn’t match.

No flaw. (D) establishes a conditional relationship (if giant redwood, then northern latitude) and correctly concludes that the sufficient condition leads to the necessary condition. The stimulus, meanwhile, concludes that the absence of a sufficient condition leads to the absence of a necessary condition, so (D) doesn’t match.

Wrong flaw. (E) establishes a conditional relationship (if can scale El Capitan, then accomplished climber) but invalidly concludes that the necessary condition (accomplished climber) leads to the sufficient condition (can scale El Capitan). The stimulus, meanwhile, concludes that the absence of a sufficient condition leads to the absence of a necessary condition, so (E) doesn’t match.