ExplanationGainsaid means contradicted, so the words that will fill in the blank will roughly mean transparent. Abstruse and cryptic both mean difficult to understand, so eliminate choices (B) and (E). Neither aesthetic, which means concerned with beauty, nor recalcitrant, which means resistant to authority, fits the meaning you need; eliminate choices (D) and (F). Both perspicuous and manifest can mean easily understood, so choices (A) and (C) produce logical sentences with the same meaning.
Hence options A and C are correct!
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