Critical Reasoning

By dating fossils of pollen and beetles, which returned after an Ice Age glacier left an area, it is possible to establish an approximate date when a warmer climate developed. In one glacial area, it appears from the insect record that a warm climate developed immediately after the melting of the glacier. From the pollen record, however, it appears that the warm climate did not develop until long after the glacier disappeared.

Each one of the following, if true, helps to explain the apparent discrepancy EXCEPT:

(A) Cold-weather beetle fossils can be mistaken for those of beetles that live in warm climates.
(B) Warm-weather plants cannot establish themselves as quickly as can beetles in a new environment.
(C) Beetles can survive in a relatively barren postglacial area by scavenging.
(D) Since planes spread unevenly in a new climate, researchers can mistake gaps in the pollen record as evidence of no new overall growth.
(E) Beetles are among the oldest insect species and are much older then many warm-weather plants.

Can someone please explain about each option?
I am facing difficulties on resolving discrepancies.

This is not a well designed question. Both choices C and E fail to explain the paradox. But on the GMAT there can only be one right answer. This question is probably from a questionable source such as 1000CR which features a lot of poorly designed questions. Practicing on questions from a questionable source can actually hurt your performance as it may positively reinforce bad reasoning.

How to get better at resolve the paradox questions?

After you read the passage, make sure you have the answers to the following 2 questions clear in your head:

1) what is the surprise (paradox)?
2) why is it surprising (paradoxical)?

Then look quickly through the choices for something that makes the surprising thing not so surprising. Beware of choices that only touch on one side of the paradox, and of choices that actually deepen the paradox.

This is from October, 1992 LSAT

Thanks Testluv for quick reply.
I am unable to understand the 4 choices that how do these resolve the paradox. However, I understood the paradox in passage.

Explanation from Kaplan
"However" signals where the "discrepancy" that we are to resolve is to be found. The topic is the use of the fossil record near a former glacier to date the appearance of a warm climate, and here's the apparent paradox: While the insect record suggests that right after the glacier melted, a warm climate appeared, the pollen record in the same area suggests that the warm climate came much, much later. (E) does nothing to explain this difference in dates: beetles may be older than "many" plants, but there could be plenty of other pollenbearing plants that are as old or that even predate the beetles. (E) is therefore irrelevant to the seeming contradiction in the stimulus, and is thus the choice we seek that does not help to explain the discrepancy.

The four wrong choices all paper over the dating discrepancy in different yet valid ways:

(A)'s solution is that the fossils were cold-weather beetles, who returned to the area while the climate was still cold. End of discrepancy: The pollen record now reigns uncriticized.
(B) explains how plants might take longer to appear in a warm area, and thus suggests why the plant fossil record might give the impression that the warming occurred later than it actually did.
(C) Since (C) shows how beetles could survive in a barren post-glacial area before the arrival of plants, it explains why the beetle fossils antedate the plant fossils.
(D) indicates that the plant record may not accurately reflect the real date of new plant growth following the melting of the glacier, which suggests that the pollen record may not necessarily accurately reflect the onset of the warm period. If this is true, the discrepancy in the fossil record is no longer surprising.

Yeah, C does resolve, my bad. I've looked at a lot of 1000CRs recently, and I missed the "postglacial" in (C).

Okay, so let's apply the strategy in my previous post to this question.

What's the surprise?...the pollen record says it got warm much later than the insect record says.

Why is this surprising?...because you would expect the two records to agree.

(A) suggests that some of the insects that appeared to be from a warm climate were actually from a cold one. Since the paradox was that the insect record says it got warm earlier, this resolves by suggesting that these were actually "cold" insects.

If the paradox is that the pollen suggests it got warm much later than the insect record does, then (B) resolves by telling us it just takes longer for the warm climate to become evident in the pollen record (than in the insect record).

As for (C), the keyword is "postglacial." So, the beetles might not be ones that returned after the glacier left; instead, they could have been there all along, thus indicating that it had yet to get warm, and that the pollen record is in fact more accurate.

So, as per (D), imagine that there are uneven planes across the landscape. A high region and a low region. A researcher looks at the high region, travels to lower ground but doesn't go low enough to see that there is more (older) pollen. So, the researcher thinks the pollen on the high region represents the oldest pollen, and so thinks it got warm later, when in fact there is older "lower" pollen that he has missed.

Hope that helped!

Shouldn't D read "plants" spread unevenly? That would make it much simpler. "Planes" with respect to the landscape is unclear.

Tani Wolff - Kaplan wrote:Shouldn't D read "plants" spread unevenly? That would make it much simpler. "Planes" with respect to the landscape is unclear.

I'm sure that's right. I just figured the plants are on the planes anyhow.

with respect to the landscape it would be "plains", not "planes"

Tani Wolff - Kaplan wrote:with respect to the landscape it would be "plains", not "planes"

indeed. it's a good thing the test doesn't test spelling. anyhow the reasoning I used in the post above would still apply just replacing the word "plane" with "plant." But good catch.