OE


crucial, requisite This is a tough question, because the sentence gives you only “subtle” as any kind of clue. Your blank should oppose it, but you don’t want the opposite of “subtle” (which would be something like obvious, which clearly doesn’t make any sense here). Instead, you need to think about the overall meaning of the sentence. Most likely, the point is that the difference between similes and metaphors is important. Null and nominal are an incorrect pair, both meaning “insignificant.” Synoptic (presenting a summary of the whole) and optional have no relationship.