Explanation

You know from the clue that human sacrifices were ubiquitous, so the act was familiar to all the tribes. The text sets up a contrast between the Mayans and the neighboring tribes in terms of their sacrificing. The trigger word while signals that the missing word goes in the opposite direction of the clue, and it must mean making the other tribes uncomfortable.

Eliminate choices (B) and (E) because those words are positive. Choice (D), expatiated, means speak about in detail and has nothing to do with the context of the sentence. Despite its topical relevance, choice (A) doesn’t contrast with the ubiquity of the sacrifices, nor does the context support the Mayans confining all the other tribes. Although choices (C) and (F) aren’t synonyms, they both fit with the given context to appropriately complete the sentence.

Hence options C and F are correct!
_________________