The argument starts by detailing the relationship between two beliefs (everyone who believes in unicorns also believes in centaurs) and then moves to a conclusion about the validity of those beliefs (because the existence of centaurs has been disproven, a belief in unicorns is also false). This commits the same flaw as the stimulus of conflating beliefs with facts because the author acts as if the existence of centaurs being disproven also disproves the existence of unicorns.

No flaw. (B) says that to believe in unicorns you must also believe in centaurs. Since you don’t believe in centaurs, we can conclude that you don’t believe in unicorns.

Wrong flaw. (C) commits the cookie-cutter “confusing necessary and sufficient conditions” flaw. It says that to believe in unicorns (the sufficient condition) you must believe in centaurs (the necessary condition). However, you don’t believe in unicorns, so (C) erroneously concludes that you don’t believe in centaurs. Negating a sufficient condition doesn’t necessarily negate its necessary condition. Alternatively, the stimulus doesn’t commit a sufficiency v. necessity flaw.

Wrong flaw. (D) addresses a relationship between two beliefs (to believe in unicorns you must believe in centaurs) then erroneously concludes that since there isn’t a “good reason” to believe in centaurs, there’s also no good reason to believe in unicorns. By definition, people don’t need a “good reason” to believe what they believe, so the argument in (D) falls apart. The stimulus, meanwhile, errs because of a mistaken conflation of facts and beliefs.

Wrong flaw. (E) starts by detailing the relationship between two beliefs (everyone who believes in unicorns also believes in centaurs) then says that because the first belief (unicorns) is unfounded, the second belief (centaurs) is also unfounded. Alternatively, the stimulus starts by detailing the relationship between two beliefs (everyone who believes in extraterrestrials also believes in UFOs) and then says that because the second belief is unfounded (UFOs), the first belief (extraterrestrials) is also unfounded.