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Argument: There is no significant difference between sea communities near oil rigs and those in control sites situated near any oil rigs. Therefore, oil rigs have no adverse impacts on sea communities.

I easily eliminated answer choices (A), (D) and (E) but fell for the trap answer choice (C), the correct answer was (B).

The principle reason for which I think I selected C was the fact that I did not do an adequate job at identifying the presupposition made by the author thus severely constraining my ability to anticipate the answer choice.

A flaw/assumption I identified as being made by the author was that he/she: "Presumed that the adverse effects precipitated by oil rigs would be projected externally and therefore would be discernable to observers", I thought to myself whilst criticizing this assumption that perhaps the oil from the rigs affected sea animals only internally (e.g., damaged their internal organs) something like that. However, the gap wasn't at all addressed in the answer choices so I guess I completely missed the ball on anticipating the answer.

Another reason for which (C) was attractive to me was the fact that it mentioned industrial effluent which I conflated with oil from the rigs. I'm habitually very abstract when reading LSAT questions to avoid making unwarranted assumptions and operating on conjecture, however in my estimation this was a perfectly reasonable assumption to make, however, feel free to correct me if you think otherwise. Indeed, while answer choice (C) conceded that the sewage and industrial effluent didn't eliminate all sea animals, it clearly stated that it reduced density and diversity by presumably killing them off which in my view clearly weakens the premise-conclusion relationship. Obviously, I'm wrong, however after mulling over this question for nearly 45 minutes, I still cannot articulate a good reason for why it is incorrect and B is correct

Edited and bumped

Premise: We compared animal communities near rigs with communities several miles from any rig and found no significant differences.
Conclusion: Rigs have no adverse affect on animal communities.

The main thing that should jump off the page here is the question, "What if both communities are being equally adversely affected?" The argument is basically assuming that because some of the communities are miles away from any rig, that they are thus unaffected by the rigs. Note, also, that the argument doesn't say anything about adverse effects on either group of communities, it just says that there weren't any significant differences. This leaves open the possibility that they were both being adversely affected.

Answer choice B basically gives you an explanation for how they could both be adversely affected despite some of them being miles away.

C does not affect the argument. All C does is explain what the adverse effects might be. But remember, the argument never actually mentions what adverse effects either group of communities had. So C is very irrelevant.

Hope that helps bro.

somethingElse wrote:Premise: We compared animal communities near rigs with communities several miles from any rig and found no significant differences.
Conclusion: Rigs have no adverse affect on animal communities.

The main thing that should jump off the page here is the question, "What if both communities are being equally adversely affected?" The argument is basically assuming that because some of the communities are miles away from any rig, that they are thus unaffected by the rigs. Note, also, that the argument doesn't say anything about adverse effects on either group of communities, it just says that there weren't any significant differences. This leaves open the possibility that they were both being adversely affected.

Answer choice B basically gives you an explanation for how they could both be adversely affected despite some of them being miles away.

C does not affect the argument. All C does is explain what the adverse effects might be. But remember, the argument never actually mentions what adverse effects either group of communities had. So C is very irrelevant.

Hope that helps bro.

Thanks a lot! This definitely helped!

No prob! One minor correction to my explanation: When I said that "The argument is basically assuming..." I wasn't quite right. The argument doesn't actually assume that. It is important NOT to assume that as you're reading it, and it obviously helps with the correct answer choice; but all you really had to realize is the other stuff I was saying regarding how just because they weren't significant differences between the two groups that neither were adversely affected.