It is clear that humans during the Upper Paleolithic period used lamps

C

More Efficient -> less time , avilable resources , desired output...

So more efficient techniques results in more number of lamps atleast by considering same amt of resources...

D

Comparison is bw the no of lamps...not bw the no of kinds..just lamps
Since earlier times ve used that kind of lamps, we dont have to find more kinds.

The question stem says that each of the following contributes to the explanation of the skewed distribution of the lamps.
ie each of the options except one will explain why greater number of lamps are associated with late Paleolithic period

Only one option should not explain why the distribution of lamps is skewed.

(A) Artifacts from early in the Upper Paleolithic period are harder to identify than those that originated later in the period,
- this explains the skewed distribution as the artifacts from Upper Paleolithic period are harder to identify so lesser number reported.
OUT

(B) More archaeological sites have been discovered from the Magdalenian culture than from earlier cultures.
- this explains the skewed distribution as more sites have been found for Magdalenian culture(dominant in late Upper Paleolithic period)
OUT

(C) More efficient lamp-making techniques were developed by the Magdalenian culture than by earlier cultures.
How does efficient lamp- making techniques explain greater number found for these lamps ?
KEEP

(D) Fire pits were much more common in caves early in the Upper Paleolithic period than they were later in that period.
- this explains that since fire pits were more common in caves in early Upper Paleolithic period so lesser number of lamps must have been used .
OUT

(E) More kinds of lamps were produced by the Magdalenian culture than by earlier cultures.
Even if more kind of lamps were used by Mag culture( dominant in later Paleolithic period) , how does it explains greater number found ?
KEEP

I can't rule out C between C & E
Please explain.

C <br /><br />More Efficient -&gt; less time , avilable resources , desired output...<br /><br />So more efficient techniques results in more number of lamps atleast by considering same amt of resources...<br /><br />D<br /><br />Comparison is bw the no of lamps...not bw the no of kinds..just lamps<br />Since earlier times ve used that kind of lamps, we dont have to find more kinds.

Sent from my CPH1701 using GMAT Club Forum mobile app

If the Magdalenians had more efficient lamp-making techniques, then they would have been able to make lamps more easily than people from the earlier period. For example, perhaps thanks to those efficient techniques, the Magdalenians were able to produce lamps twice as fast as the earlier people. This could certainly help explain why a greater number of known lamps is associated with the Magdalenians, so (C) can be eliminated.

The "kinds" in answer choice E is the telling factor here.

Let's assume they produced large and small lamps with various shapes and colors.
That is all nice and beautiful, however just because they produced different types of lamps we are not given any indication that the Magdalenians also produced large numbers!

While some fancy stores might offer more different kinds of pillows than Walmart does, there is a good chance that the sheer number of pillows offered is bigger for Walmart than it is for the small, fancy pillow store.

Hope this helps and best regards,
Chris

Can some one explain why A is wrong ?

(A) Artifacts from early in the Upper Paleolithic period are harder to identify than those that originated later in the period,

My reasoning : Since lamps were difficult to identify , therefore the reported numbers are more likely to be skewed.

humans used lamps through the entire Upper Paleolithic (UP) period, but the distribution of known lamps is skewed towards the late UP, when the Magdalenian (M) culture was dominant.
Type - Explain except

(A) DOES help to explain the result. If artifacts from earlier in the period are harder to identify, then it makes sense that we would not be able to identify as many lamps from earlier in the period. This would explain why we've identified more lamps from later in the UP. Thus, this answer is incorrect, as we're looking for the answer that does NOT help to explain the result.

(B) DOES help to explain the result. If we've identified more archaeological sites from later in the UP (when the M's were dominant), it's likely that we'll find more artifacts from later in the period. Imagine that we've identified 5 sites from the early UP, and 10 from the late UP. If we find one lamp at each site, we'll find 5 early lamps and 10 later ones. This would explain why we've identified more lamps from later in the UP. Thus, this answer is incorrect, as we're looking for the answer that does NOT help to explain the result.

(C) DOES help to explain the result. If the M's could make lamps more efficiently, then it's likely that they made more lamps than cultures from the early UP. This would explain why we've identified more lamps from later in the UP -- in fact there were more lamps! Thus, this answer is incorrect, as we're looking for the answer that does NOT help to explain the result.

(D) DOES help to explain the result. If fire pits were more common in the early UP, then early cultures were probably using fire pits for light instead of lamps. This would explain why we've identified more lamps from later in the UP. Thus, this answer is incorrect, as we're looking for the answer that does NOT help to explain the result.

(E) DOES NOT help to explain the result, and is therefore the correct answer. Even if the M's produced more kinds of lamps, this doesn't necessarily mean they produced more lamps overall. Imagine I like to bake cookies. Sometimes I bake chocolate chip, sometimes oatmeal, sometimes sugar cookies, holiday cookies... the list goes on and on. I bake lots of different kinds of cookies, but this doesn't mean I bake more cookies than Nestle Tollhouse, who bakes only chocolate chip cookies. Just b/c the M's made a bunch of different kinds of lamps doesn't mean they made any more lamps than previous cultures. Thus, this doesn't help to explain why we've found more lamps from the later part of the UP.

Your reasoning is fine! If lamps from early in the period are harder to identify, then we should expect the kind of skewing described in the passage. That means that choice (A) contributes to the explanation provided in the passage.

However, the question asks us which choice does NOT contribute to the explanation. Since (A) supports the explanation, we must eliminate it and look for a choice that does NOT support the explanation. So I think you made the most common mistake on EXCEPT questions: you found something that was relevant, but you should have eliminated it, instead of accepting it as the right answer.

To avoid that error, here's what I'd generally recommend on EXCEPT questions: in huge letters on your page, write "cross out anything that ________", so that you don't get confused. So in this case, you'd write, "cross out anything that contributes to an explanation of the skewed distribution of lamps." (A) definitely contributes to the explanation, so you can cross it out.

I hope this helps!

Why is E correct here and not D?

Can someone provide me a reasonable explanation. Can we expect these kinds of questions on official GMAT?

Yes you certainly can, this can be a 700+ level question.

E is correct because different types of lamps has nothing to do with number of lamps, variety vs count, if you want a lamp you will buy a lamp, variety will not affect the usage and hence it does not explain why there were more lamps in that period.

Hope it's clear.