In Evaluate questions, the answer choices will come as questions that can usually be answered Yes/No or High/Low. For the correct answer choice, at least one of those answers will have an impact on the argument one way or another. Maybe answering “yes” to the question will weaken the argument, for example, or maybe answering “very few” to the question will strengthen.

As with strengthen and weaken questions, then, our goal in approaching the stimulus is to read critically and identify a gap between the argument’s premise(s) and conclusion(s).

This question involves a type of causal reasoning we call “phenomenon hypothesis”: the premises lay out some observations about the world (e.g. “I saw a bunch of birds flying south.”) and the conclusion offers a potential explanation for that phenomenon (e.g. “They must be fleeing a hoard of bird-eating godzillas.”)

The phenomenon hypothesis pattern spans a bunch of question types, but whenever you see it the broad approach to anticipating the answer is similar: brainstorm some alternate explanations for the phenomenon (“maybe they’re just flying south because winter is coming”), and poke holes in the explanation presented to you (“there’s no such thing as bird-eating godzillas”).

This question’s argument fits the phenomenon hypothesis pattern – it presents some facts, and a conclusion about those facts. (The “however” and “since” rhetorical cues, by the way, make identifying the conclusion straightforward.)

Context 1: Last year we banned phosphates.
Context 2: Some people got around the ban, though.
Premise: But phosphate pollution from the treatment plant is way down.
Conclusion: Some people must still have switched away from phosphates.

We undermine phenomenon hypothesis arguments by posing ourselves a riddle: in what world could all the facts be true, but the conclusion still isn’t true?

Here, our job is to imagine a world in which pollution from the treatment plant is down, but no one switched away from phosphates. So we’re mainly looking for additional factors that would explain the decrease even if no one switched detergents.

Perhaps the plant handles way less volume than it used to. Perhaps other sources of phosphate pollution dropped dramatically this year. Perhaps (spoiler alert) the plant became more efficient at treating phosphates. Noodle on this a bit before moving to the answers – it’ll help you recognize the right one when you see it.