Logical reasoning PrepTest 119 · Section 3 · Question 6

Incorrect. The conclusion is about the palatability of the water, not the safety of it, so this answer is out of scope.

Incorrect. While this answer doesn't establish the conclusion since it's about what is "expected" and not what will happen, it aligns with the conclusion and is thus more of a strengthener than a weakener.

Incorrect. The argument's conclusion is qualified—it's based on "continuing the salting of Albritten's roads at its present rate." It makes a prediction based on that being true. If anything, this answer suggests it will be true, and thus it's more aligned with the argument than against it.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
20 years ago - Albritten started using heavy salting to deice roads
Now - Groundwater is at 100mg salt/liter
Now - Other areas that don't use salt have groundwater at about 10mg/liter
Water at 250+mg/liter is too salty
Therefore - If the salting continues, the water will be too salty in a few decades

Answer Anticipation:
This argument has quite a few comparisons, so it's important to unpack them and see which ones are relevant, and if there are any flaws associated with them.

First, the argument jumps from 20 years ago to today. It suggests that the heavy salting is similar between those time periods ("began around" suggests it's still happening). It brings up the current salt levels in groundwater, but it doesn't compare those levels to what they were 20 years ago.

Instead, it compares them to what those levels are in other towns that don't use salt currently. While the levels in Albritten are much higher, that's not necessarily because of the salt used for deicing—maybe Albritten is just located on top of a salt deposit!

Since the argument is about the heavy salting causing an increase in the concentration of salt in the groundwater, the relevant comparison is between salt levels in Albritten now and 2 decades ago, not between Albritten and other towns today. The comparison provided doesn't support the conclusion, but there is a comparison that would—if the salt levels 20 years ago were 10mg/liter, then the 90mg/liter increase would suggest a trend towards breaking 250mg/liter in the next few decades.

As such, we can weaken this argument by bringing up a comparison that shows the heavy salting hasn't resulted in a large increase—if the salt levels in groundwater were somewhere around 100mg/liter 20 years ago.

Answer Explanation:
If 20 years of heavy salting increased the concentration of salt in the groundwater by 10mg/liter, it's going to take a long time to get up to 250mg/liter that makes water unacceptably salty (500 years or so, if our math is correct). That's much longer than the prediction of it happening in the next few decades.

Key Takeaway:
When an argument is based on comparisons, work through them to identify what is being compared and if that comparison is related to the conclusion. Frequently, when there are multiple points of comparison, some won't be directly related to the conclusion. They're there to throw you off from the comparison that would actually support it!

Incorrect. The conclusion is conditioned on the salting continuing at its current rate. Stating that the condition won't be met doesn't weaken the conclusion. To see a parallel example, think about a conclusion saying, "If you poke a beehive, you will get stung." Not poking the beehive doesn't weaken that connection—it just means you won't necessarily get stung!