PrepTest 139, Section 4, Question 20

What we’re looking for

Working the answers

• A

  “Largely responsible” claims a substantial share of the explanation. The passage doesn't measure pollution's contribution, and it reports scientists' belief about the enhancement rather than establishing the entire chain unconditionally. A turns a possible contributing influence into a major established cause of the fires' size and intensity.

• B

  Greater susceptibility to fire doesn't mean that without the stronger El Niño there would have been few or no large fires. Even if a factor increased a hypothetical fire count from 50 to 100, removing its influence would leave 50, not necessarily “few.” Those numbers aren't facts about 1997; they show why an influence on an outcome doesn't establish this drastic reduction.

• C

  We have information about this unusually strong El Niño and the 1997 fires. That doesn't establish a general rule about the size and intensity of tropical fires whenever El Niño is strong. Other years could differ in ways the passage never discusses.

• D

  The scientists are described as believing that pollution-related warming enhanced El Niño. We aren't told that they also believe the stated connections to drought and fires, or that they have drawn the further conclusion about the fires' size and intensity. We can't assign them an additional belief just because we can consider how the passage's statements fit together.

• E
  Correct

  This stops at drought rather than carrying the inference all the way to the fires I initially focused on. The unusually strong El Niño caused the widespread drought. If pollution enhanced that El Niño's strength, then pollution contributed to the drought through that effect.

  The “if” matters: E doesn't require us to treat the scientists' belief as already proven. It explains what follows if the pollution link is true, without claiming that pollution was the main cause or quantifying its contribution.