http://classic.7sage.com/lsat_explanations/lsat-64-section-1-question-22/
The following is my reasoning for why the answer to PT64S1Q22 is D, and is not B. The answer-sheet states that the answer is B, while online explanations for why the answer is B seem to me to be confusing, non sequitor, flawed, and specious. That being said, im likely wrong, and the LSAT writers and expert teachers are likely right, and I simply currently cant see why. PLEASE someone explain to me how my reasoning is flawed, and why B is correct. THANKS!!
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Summary: The arguments conclusion incorrectly points to a cause (using the word "promoted"), based on a correlation. B indicates a correlation, not a cause, so B doesn't strengthen the argument. D, however, points to a cause (an indirect cause), helping to justify, and thus strengthen, the argument. D is therfore the correct answer.
Argument in Question Stem, presented in syllogistic format:
Sewage sludge concentrated with heavy metals = C
Surviving bacteria of C are resistant to heavy metal poisoning = Rh
Surviving bacteria of C are resistant to antibiotics = Ra
• C
• Rh
• (C --> Rh) (relationship is causal)
• Ra
☆ therfor, (C --> Ra) (relationship causal)
Flaw: The correlation of Ra, C, and (C --> Rh) does not mean there is a causation from C to Ra. The answer which strengthens this argument will show that (Rh --> Ra) (C causes Ra because it causes Rh which causes Ra) or directly that (C --> Ra) (C causes Ra) or some contrapositive to that effect (~Ra --> ~C) or (~Ra --> ~Rh)
Answer choices, presented in syllogistic format:
A) (~Ra --> ~Rh) with a correlative relationship, not causal. Also uses the word "most" further discrediting a potentially causal relationship. Wrong answer.
B) [(~C --> ~Rh) & (~C --> ~Ra)] with correlative relationships. Even if they were causal, it at most only proves the latter relationships contrapositive that (Ra --> C, relationship causal) which in no way strengthens the claim that (C --> Ra) for the existence of a causal relationship in one direction in no way indicates that such a relationship exists in the opposite direction. Wrong answer.
C) (Ra --> Rh), relationship causal. This doesn't tell us that (Rh --> Ra) for the existence of a causal relationship in one direction in no way indicates that such a relationship exists in the opposite direction. Wrong answer.
D) (C --> A), whereas the relationship is correlative and A = the presence of significant concentrations of antibiotics. This isn't the ideal answer, clearly. However, it introduces a new player (A), which in turn offers a prospective causal link. If (C --> A) then it's possible that (A --> Ra) which would obviously mean that (C --> A). Though we don't know to what degree it's possible that (A --> Ra), the existence of this new possibility is real; indeed, it makes sense from outside knowledge that higher levels of antibiotics in a medium likely means that the only bacteria who will survive are those that are resistant to antibiotics (duh). This renders the reasoning in the argument much stronger. Correct answer.
E) [(~Bs --> Rhp) & (~Bs --> Ra)] definitely wrong because it's completely changing the subject matter.
So what's my Achilles heal here?
