PrepTest 103, Section 4, Question 19

What we’re looking for

Working the answers

• A

  We aren't given a comparison with other marine animals. Hearing only about dolphins doesn't establish that brevetoxin affects them through a different biological mechanism.

• B

  This might sound like a way to explain the Gulf comparison: perhaps the alga is more toxic outside its usual habitat. But the research team never supplies that toxicity comparison. An idea that could patch a problem in a theory isn't automatically something the theory supports.

• C

  The team's explanation of this disaster doesn't establish what is “usually associated” with opportunistic infections. It describes a proposed connection here, without showing how often brevetoxin is involved in such infections generally.

• D

  The account doesn't attribute the thin condition to PCBs rather than brevetoxin. Brevetoxin is the proposed starting cause, and PCBs released during blubber loss worsen the dolphins' condition. We aren't separately told exactly why the dolphins lost weight, much less that PCBs caused it instead.

• E
  Correct

  Releasing stored PCBs “further exacerbated their condition”—made it worse. That supports the comparison: released PCBs may be more dangerous than PCBs still stored in the fat. We don't have to assume the stored pollutants were harmless. The reported worsening upon release is enough to support greater danger.