Q1 - The water of Lake Laberge

[ManhattanPrepLSAT1]

We need to explain how Lake Laberge could contain high levels of toxaphene even though toxaphene has been banned in North America since the 1980’s.

Correct Answer
We know that toxaphene is a pesticide. Answer choice (A) could explain how toxaphene would be present in Lake Laberge for pesticide levels remain high, decades after their use ends.

Incorrect Answers
(B) fails to explain how such pesticides in addition to toxaphene could be present for their use was halted in the 1980’s.
(C) eliminates one way that toxaphene could have ended up in Lake Laberge without being used in North America _ this only makes matters more puzzling.
(D) is irrelevant. So long as those manufacturers complied with the ban, whether or not they supported the ban is irrelevant.
(E) is irrelevant. How would toxaphene get into those organisms without the use of toxaphene?

[JinZ551]

We need to explain how Lake Laberge could contain high levels of toxaphene even though toxaphene has been banned in North America since the 1980’s.

Correct Answer
We know that toxaphene is a pesticide. Answer choice (A) could explain how toxaphene would be present in Lake Laberge for pesticide levels remain high, decades after their use ends.

Incorrect Answers
(B) fails to explain how such pesticides in addition to toxaphene could be present for their use was halted in the 1980’s.
(C) eliminates one way that toxaphene could have ended up in Lake Laberge without being used in North America _ this only makes matters more puzzling.
(D) is irrelevant. So long as those manufacturers complied with the ban, whether or not they supported the ban is irrelevant.
(E) is irrelevant. How would toxaphene get into those organisms without the use of toxaphene?

I would rather say answer choice B is irrelevant to the argument, because whether or not it contains pesticides "besides" toxaphene has nothing to do with explaining the paradox