Tricky one, but I would pick A.

Guys, I havent really started studying CR and this is the first time I've come across a question stem like the one mentioned here.

Which of the following would it be most useful to determine in evaluating the argument? -- Does this mean weaken/undermine the argument in this question??

Seems to be A for the reasons mentioned above.

rapid depletion on land will make the extraction from seawater a necessity and hence commercially viable.

i"ll go with A...
This Q is about evaluating the argument, If uranium in deposits on land is not rapidly being depleted, then y we should be bothered about technology advances and extracting uranium from seawater

i can't understand why A is the answer.. i would choose this option only in a "weaken question", but this is an "evaluation question"; my kaplan book says: "The correct answer won't strengthen or weaken the author's reasoning or supply a missing assumption. Instead, the right answer will specify the kind of evidence that you would help you to judge the validity of the author's argument"
this is the reason why i'd chose C
can someone helps me?

Well this is a toughie.Two options are too close.
Fact 1: Most of the world's supply of uranium currently comes from mines
Fact 2: It is possible to extract uranium from seawater, but the cost of doing so is greater than the price that uranium fetches on the world market.
Conclusion: until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable

A. Whether the uranium in deposits on land is rapidly being depleted
CORRECT.If the uranium in deposits on land is rapidly being depleted then we have no other choice to shift to some other source .Doesn't matter what the cost of extraction is !
B. Whether most uranium is used near where it is mined
Out of scope. We are concerned about price of extraction not transportation cost or any other thing that this argument is hinting.
C. Whether there are any technological advances that show promise of reducing the cost of extracting uranium from seawater
Incorrect.This is tempting.But i believe the argument is made now so we have to check the validity NOW.The future techs are out of scope.
D. Whether the total amount of uranium in seawater is significantly greater than the total amount of uranium on land
Irrelevant. It doesn't matter how large quantity is available in seawater.If the cost of extraction is high,we will not fetch it.
E. Whether uranium can be extracted from freshwater at a cost similar to the cost of extracting it from seawater
Out of SCOPE.This introduces a new source.We need to evaluate seawater only.
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Found a very nice explanation on manhattangmat.
here is the link for that http://www.manhattangmat.com/forums/mos ... t3508.html

whoa, no, guys. that's not the issue here.

the problem is this:

the argument says
until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable.

in other words, the argument is saying that the ONLY WAY that seawater extraction will be commercially viable is if the cost of that extraction comes down.

to weaken the argument, then, you need to find ANOTHER way in which seawater extraction will be commercially viable, WITHOUT a cost reduction.
this is what choice (a) does. if the uranium on land is being depleted, then extracting uranium from seawater will become "commercially viable", out of pure necessity. the cost will go up, but that's the breaks.

choice (c) doesn't actually affect the argument at all, because the argument already acknowledges that uranium will become commercially viable IF the price comes down.

--

analogy:
if i tell you this:
unless you eat my fish 'n' chips, you'll never know the true meaning of gastronomic ecstasy

then:
* if you say "eating your fish 'n' chips will give me gastronomic ecstasy", then that doesn't affect my statement at all, because you're just echoing what i've already told you.

however:
* if you say "au contraire, i can also get gastronomic ecstasy from a nice fat slice of meat lover's pizza", then that weakens my argument, because i'm telling you there's only one source of gastronomic ecstasy but you're countering with another.

substitute
fish 'n' chips --> cost increase
pizza --> depletion of land resources
gastonomic ecstasy --> commercially viable
...and there you have it.
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This is a great question and I just want to add my two cents to clarify the difference between A & C. I picked A first and then started thinking about C which also makes a lot of sense. But here's my reasoning for why C is definitely wrong.

A) Correct answer because, if land deposits are running out in 10 years then extracting from seawater becomes a necessity. At that point think about supply and demand, when the supply decreases, demand increases and the price goes up. Therefore at some point it becomes commercially viable. Now think about OIL, when the price of oil is $40 a barrel, it becomes commercially unprofitable to dig oil out of Alberta's tar sands, so companies stop extracting it. But when the price goes up, they start extracting because it becomes commercials viable. Demand has a huge impact on the price. Now imagine if all the Oil in the world ran out and we found oil on the Moon, would it become commercially viable to go to the moon? Yes, people would start going to the Moon to get oil. So think about that.

For C) many people are stuck with this option, I also thought this might be correct BUT, think about the supply. IF the supply of land uranium is unlimited, it will never run out, so even if there's new technology then that technology might make it cheaper to extract from land. (There is a lot of uncertainty). So think in terms of extremes, unlimited resources on land, therefore we may never have to extract from water, even if it becomes cheaper than it was before. Say Extracting from land = $1, and extracting from water = $10, even if the cost of extracting from water comes down to $5 with new technology, its still cheaper to get it from Land. So without knowing the cost of each method and supply, we can't answer with C.

So the answer is A. Hope this helps!
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why not (b)? since most of the uranium is used where it is mined then there can be reason to extract uranium at those places where there are no mines to meet the local demand making it commercially viable.

You mentioned that we need to evaluate along the COST, PRICE line. In that case why is C wrong which says the the cost will decrease based on technological advancements