The drought in the central part of the country is estimated

A - slightly out of context.
B - possible.
C - possible.
D - possible.
E - out of context. no mention of politics in the passage.

Basic POE gives me B, C, and D. I have a 33% chance of nailing this problem...

Looks like we can knock C out of the running. We could experience inflation without a two year drought.

So 50% chance.

Looks like B will be the answer as the conclusion of the passage does indeed imply that irrigation is the only solution.

OA...B
yay!

The argument evaluation:

The drought reduce this year's national corn harvest by more than normal level => increase meat and other foods prices by 17% in one year, 20% in two year.
Therefore, irrigating the largest affected corn fields will avert severe inflation latter

A. other American agricultural areas are also not expected to meet their anticipated corn yields this year=> out of scope
B. irrigation is the only way that the national corn yield can be significantly increased
C. the heat wave and drought will persist through the next two years => irrelevant
D. irrigation will insure that corn harvests reach normal levels
E. it is politically feasible for government authorities to spend money irrigating fields at the present time => out of scope

Only choice B and D are the contenders. Negating choice B and D, we will have:

B. Irrigation is not the only way that the national corn yield can be significantly increased => the argument is corrupted.
D. Irrigation will not insure that corn harvests reach normal levels => the conclusion of the argument does not mention whether or not the national corn yield will reach the normal level, but avert (stop) the inflation that is increasing.

=> choice B is the correct one.

With this kind of question, we can see how important the argument's conclusion is. So, learn to understand completely the argument's conclusion.

Straight (B)
..." either we spend a small amount now to irrigate the largest affected corn fields and avert severe inflation later, or else fail to irrigate now and insure inflation later"

Means:- The dependency of a good crop depends solely upon the irrigation.

So,to increase the corn yield , irrigation is the only ideal option .

Initially chose D. But then on re-reading made me understand my mistake: I missed normal levels.
For those who are on same lines on which I was earlier, here is the easy solution. In the premise, its stated that the corn levels have reduced to one third of their normal levels. Let the normal level be 100. Now negate B, we get that irrigation will ensure that corn harvests don't get to their normal level. What if the corn harvests reach upto 99, then the conclusion doesn't fall apart.
but if there are several other ways that the national corn yield can be significantly increased, then even if we don't spend much on irrigation then also we can't ensure inflation. The conclusion falls apart and hence the answer is B.

I chose "C" first but on re-reading, B makes complete sense.

The drought in the central part of the country is estimated to reduce this year's national corn harvest by more than one-third from its normal levels. Such a shortfall would subsequently increase meat and other food prices by about 17% in one year and 20% in two years. So, either we spend a small amount now to irrigate the largest affected corn fields and avert severe inflation later, or else fail to irrigate now and insure inflation later.

The argument is valid only if

A. other American agricultural areas are also not expected to meet their anticipated corn yields this year -Okay, let them not meet their target. Out of scope.
B. irrigation is the only way that the national corn yield can be significantly increased -The conclusion says that either irrigate the fields and decrease the inflation or suffer at the hands of increased inflation. It means that only irrigation can decrease the inflation.
C. the heat wave and drought will persist through the next two years -Okay, it is a fact set. Out of scope
D. irrigation will insure that corn harvests reach normal levels -Nowhere in the argument it's written that the harvests will reach normal levels. Out of scope
E. it is politically feasible for government authorities to spend money irrigating fields at the present time -Out of scope

The conclusion comes after the keyword “so.” The author believes that if money is spent to irrigate corn fields, inflation will be averted. If money is not spent to irrigate, inflation is a given. The author's evidence is that there is a drought now that will reduce the corn harvest, which will increase food prices over the next two years.

Predict the Answer:

Note the chain of causation in the evidence. Drought leads to corn shortfall, which leads to increased corn prices, which leads to increased food prices. The author focuses on avoiding the corn shortfall and concludes that the corn fields have to be irrigated. The author must believe that irrigating the corn fields is the only way to avoid the corn shortfall.

Evaluate the Answer Choices:

(B) is a perfect match for the prediction arrived at in Step 3. The author must believe there is no other way to increase the corn yield besides irrigation. (B) is the answer.

(A) is irrelevant. The author focuses on the central part of the country, and the effect the drought in that part of the country will have on the economy. What will happen in other areas has no impact on the author's argument. Eliminate (A).

(C) is not something the author must be assuming. The entire argument is about the effects of the current drought, regardless of how long it lasts into the future. Eliminate (C).

(D) is extreme. The author doesn't have to assume that irrigation will ensure corn harvests reach normal levels. The author is concerned because the drought will reduce the corn harvest “by more than one-third from its normal levels.” The author believes irrigation will solve the problem, but that doesn’t have to mean normal harvest levels. Perhaps irrigation will bring the harvest to 75% of normal levels, or 85%, and that this would be enough to solve the problem. Eliminate (D).

(E) is irrelevant because the author doesn't care who will or could pay for the irrigation, just that if it is done, inflation will be avoided, and that if it isn't done, inflation will come. Eliminate (E).

TAKEAWAY: Be very clear on the evidence and conclusion of the argument, and stick to the connection between them. Irrelevant choices are quite common and can be easily spotted by having a good paraphrase of the argument.

Can someone please explain why option (D) is not the answer when in contrast to option (B).

The conclusion "either we spend a small amount now to irrigate the largest affected corn fields and avert severe inflation later, or else fail to irrigate now and insure inflation later." talks about the amount of money being spent on irrigation to prevent inflation or to pay the money later in effect of the inflation.

How does Option (B) mentioning that irrigation is the only way to get the crops to the normal level help in explaining the amount of money spent, which is nothing but the conclusion.

in B]: I am unable to digest the word 'significantly' Isn't the choice too extreme.

why there is a need to assume significant increase in corn yields. Normal level yield will also suffice

Significant is actually the polar opposite of 'extreme'—it's the most understated thing we can possibly say about a thing that's actually a thing.
Literally, anything that isn't negligible/insignificant is "significant".

(Consider what "statistically significant" means. It doesn't mean huge or extreme—it just means that some phenomenon is distinct enough that it's probably not the result of pure randomness.)

This meaning—"big enough not to be insignificant/negligible"—is the absolute minimum that's required for the reasoning here to work. Accordingly, it's exactly the quantifier we want to see here.

I am checking the reply box for the first time

KarishmaB GMATNinja

How to choose b/w B & D? I cannot gauge which one's better?

This is an assumption question. Only if "assumption," then the argument is valid.
So we are looking for a necessary condition for the argument.

The conclusion is "Either irrigate and avert severe inflation or don't irrigate and face inflation"

"Either or" means one or the other will certainly happen. So there is NO third option. Which means that irrigation is necessary to avert severe inflation (by significantly increasing corn yield). It means there is no other way in which corn yield can be increased significantly (say, putting more fertilizer will not increase corn yield significantly)

B. irrigation is the only way that the national corn yield can be significantly increased

As discussed above, (B) makes sense. Negate it: Irrigation is not the only way to increase corn yield significantly.
Then our conclusion falls apart. Not irrigating may not lead to inflation later.

D. irrigation will insure that corn harvests reach normal levels

Irrigation doesn't need to ensure that corn harvests reach "normal levels." We said "irrigate to avert SEVERE inflation". This means that irrigation will increase the corn yield enough to avert severe inflation. Inflation may still be there; normal levels of corn yield may still not be achieved.
We don't need option (D) to be true.

Hence it is not the answer.

Answer (B)