One year ago, a municipality banned dishwasher detergents containing phosphates. Anecdotal evidence indicates that ma...

Ravi on June 9, 2019

@claire_crites,

Happy to help. Let's take a look at (C) and (E). We're looking for an
answer choice that'd help us evaluate the argument in the stimulus.

(E) says, "Did municipal officials try to stop people from bringing
detergents containing phosphates into the municipality?"

The problem with (E) is that the argument admits that many people did
not change detergents even though ones with phosphates were banned.
The question we're concerned with is whether or not the reduced
phosphate pollution from the municipal wastewater treatment plan
implies that some residents did change detergents. Thus, (E) is out.

(C) says, "Were any changes made in the past year to the way the
municipality's wastewater treatment plant treats phosphates?"

(C)'s question is very important in evaluating the argument because it
identifies a potential alternative cause. If the municipality's
wastewater treatment plant changed the manner in which it treats
phosphates, then this might be able to explain the reduced phosphate
pollution, which would weaken the argument. If the plant didn't change
how it treats phosphates, then this would rule out one alternative
cause and would thereby strengthen the argument. Thus, (C) is the
correct answer choice.

Does this make sense? Let us know if you have any more questions!