A difficult Text Completion can be difficult for a number of reasons: esoteric vocabulary, twisted sentence structure, seemingly imperceptible nuances in answer choices. Indeed, some of the most difficult Text Completions are a sinister blend of all three. Nevertheless, there is another type of Text Completions that in some ways may be even more difficult, and diabolical.
One of the objectives in successfully answering a Text Completion is to choose answer choices that create a complete, coherent meaning. That is if you choose a word that works for the first blank but no answer choice fits in the second blank, then the word you picked for the first blank is likely incorrect.
At this point, you may find yourself working backwards, plugging in answer choices to create a paragraph (or sentence) that has a coherent meaning. While plugging-in will get you nowhere, if, even after looking for keywords in the sentence, you find yourself unable to come up with an answer, then you must use a different strategy. So once you’ve thought a bit through the sentence, plug in the different answer choices to see if you can create a sentence that makes sense.

Below is a challenging Text Completion. See if you can come up with the correct answer.
James Maxwell once remarked that the best scientists are the (i) _______ ones; not hemmed in by the (ii) ______ of their respective fields, they are able to approach problems with a(n) (iii) _______ mind, so to speak.

(i)
(A) adaptable
(B) revolutionary
(C) ignorant

(ii)
(D) myopia
(E) preconceptions
(F) inertia

(iii)
(G) fertile
(H) rational
(I) empty

Explanation:

Here it may be tempting to read the sentence and plug in (A) or (B). Both answers make sense. In fact, you could construct a legitimate sentence using (A) and (D)/(E) or (B) and (D)/(E). However, how would you create a coherent sentence with the third blank?
Neither fertile nor rational are really back up by clues in the passage. Not being limited by their field’s way of thinking doesn’t quite imply a fertile mind. More likely, having a mind that is not stuck in a certain way of thinking would be one that is empty. You may argue that empty mind is too negative, but notice the words ‘so to speak.’ This is a phrase that translates to “metaphorically.”
Completing the third blank with ‘empty’ allows us to work back through the first two blanks. We want scientists with an empty mind, thus (C) ignorant works best.
To be ignorant of what is going on in a specific field is not to be hemmed in by the preconceptions. Scientists are free to approach a problem on their own terms, learning as they go.

Takeaway

This is obviously a sophisticated thought being conveyed, and a tough question to boot. Remember, a question like this is only for the 160+ Verbal scorers. But if you hope to get all the Text Completions right, you will have to contend with questions just as twisted as this one.