ankur_1988, the key to understanding why (B) is the correct answer is correctly interpreting the question, which is written in a kind of confusing way. Let's break the question down:

**Quote:**

Which of the following, if true, could best be used as a basis for arguing against the author's position that the meteorologists' claim cannot be evaluated?

- First, we have the "meteorologists' claim": "if only they could design an accurate mathematical model of the atmosphere with all its complexities, they could forecast the weather with real precision."
- Then, we have the "author's position" about the above claim (as stated in the question): "the meteorologists' claim cannot be evaluated."
- How does the author reach that position? By stating that: "any inadequate weather forecast would obviously be blamed on imperfections in the model."

Now we are asked to find an answer choice that could be used to argue

against the author's position. So, we need evidence that the meteorologists' claim

can be evaluated. With that in mind, let's go through the answer choices:

**Quote:**

(A) Certain unusual configurations of data can serve as the basis for precise weather forecasts even though the exact causal mechanisms are not understood.

Answer (A) provides information about how the mathematical models are constructed, but does not allow us to further evaluate the claim of the meteorologists. Because it does not answer our question, we can throw (A) out.

**Quote:**

(B) Most significant gains in the accuracy of the relevant mathematical models are accompanied by clear gains in the precision of weather forecasts.

This answer shows a measurable relationship between mathematical models and the precision of weather forecasts. Establishing this relationship makes it possible to evaluate the meteorologists' claim, because the trend provides evidence for expected future results. Answer (B) is looking good.

**Quote:**

(C) Mathematical models of the meteorological aftermath of such catastrophic events as volcanic eruptions are beginning to be constructed.

Does this answer choice assist in evaluating the meteorologists' claim? We are concerned with weather predictions in general, not with the results of certain catastrophic events. Overall, answer (C) does not provide information that argues against the author's claim. (C) is out.

**Quote:**

(D) Modern weather forecasts for as much as a full day ahead are broadly correct about 80 percent of the time.

This answer choice does not specify if modern weather forecasts are more accurate than previous forecasts, or even whether these forecasts are using the mathematical models at the heart of this question. Without additional context, this option does not help in evaluating the meteorologists' claim. Throw answer (D) out.

**Quote:**

(E) Meteorologists readily concede that the accurate mathematical model they are talking about is not now in their power to construct.

In the passage, the meteorologists state that

"if only" they could create a more complex model, they could predict the weather with more accuracy. So, they already admit that the model is "not now in their power to construct," as written in answer choice (E). The claim that we are attempting to evaluate deals with

future models and associated predictions, not with

current capabilities. Option (E) does not provide evidence one way or the other on the meteorologists' claims, and so is not our answer.

Answer (B) is correct.

_________________