Logical reasoning PrepTest 109 · Section 3 · Question 20

Incorrect. First, this answer disconnects craving fatty foods (the conclusion) from eating fatty foods (the premises), so it would cut against the argument, if anything. However, it's too weak to even do that in stating that the two aren't invariably linked—they could still be very strongly linked even if the rats prefer the lean foods on occasion.

Incorrect. The closest this answer could come to strengthening the argument is eliminating an alternative cause—fat in the brain. However, there's no suggestion that fat in the brain has anything to do with dietary preferences, so this answer fails to establish that it provides evidence against a potential alternative cause. Alternative causes have to have some link to the effect—either inherent to the concepts/definitions, or defined in the stimulus or answer. This one doesn't have any of those!

Incorrect. How the chemical components of G relate to those of different types of food can't be known to be relevant since the stimulus doesn't discuss this chemistry.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Study — Rats with higher concentrations of G were also more likely to pick fatty foods over leaner ones
Conclusion — G causes cravings for fatty foods in rats

Answer Anticipation:
Strengthen questions very frequently feature correlation/causation flaws and the conclusion here being explicitly causal should have tipped you off that this question falls into that category. You also could have noted the correlation in the premises (were found to have) or seen that the argument was based on an experiment which frequently sees correlations that are then used to support causation.

In any case since this argument features a correlation/causation flaw we should look for the standard answers:
(1) Eliminate an alternative cause
(2) Find more examples of G and a preference for fatty foods going together
(3) Find a control (no G no preference for fatty foods) though this was already established in the stimulus by comparing rats with high and low levels of G

Answer Explanation:
This answer establishes that the timeline makes sense for the G to be the cause of the preference for fatty foods (and not the effect or unrelated). Causal relationships are inherently temporal with the cause needing to predate the effect and so this answer strengthens the argument by establishing that to be the case here.

Key Takeaway:
Always be on the lookout for correlative/causal language in Strengthen questions. It's—by far—the most common flaw in this question type and it leads you to anticipate specific answers.

Incorrect. This answer relates the metabolization of fat, not the consumption of fat, so it doesn't directly affect the argument. And, if anything, it would suggest that eating the fatty foods comes first, followed by the high concentrations of G, which would provide evidence for reversed causality and weaken the argument.