Critical Reasoning

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
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
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

The OA is B. I think its D.

Can someone please point out why D is wrong and the logic behind this.

The two responses do appear very close in meaning. The difference seems to lie in the different wording: 'national corn yield' versus 'corn harvests'. To avert the national problem we need to insure that the national yields increase. D is not sufficiently specific an assumption - it might pertain only to some of the harvests, not to the aggregated national yield.

Thanks for posting such a good question. Was lucky though!

Experts, please help us understand the reason to choose B over D.

I like this very much. This shows RESTATE EVIDENCE answer choice.

D and E are RESTATE EVIDENCE choices. IT IS HARD TO REALIZE THESE CHOICES.

this kind of answer choice is tricky for assumption and strengthening questions. This trick is very popular on gmatprep, the only official source of hard question but not popular in OG books.

the conclusion is that we can irrigate and get good harvest or do not irrigate and get inflation

this mean when we irrigate, we have good harvest. This is evidence already. D restate evidence.

I thought D is far extreme than B although 2 choices have the same level of certain. The difference here is D certain about the normal level yield, B is certain the increase (B not sure the increase will reach the normal level). Also, the conclusion stated that "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 most valuable word here is "avert severe inflation" (not avert totally inflation". Hehe, this is my habit, always stick to conclusion with CR questions.

Beside, I thought (and quite sure) that the difference between words as Ilana@MasterGMAT mentioned is acceptable.

Am I correct? Ilana@MasterGMAT, can you evaluate my reasoning?

Good Question.....I could reach to B and D....But since the answer choices were not hidden using a spoiler, I saw the answer before by mistake....

Can I request everybody to hide the OAs using spoiler.

Thank you!!