35.

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

Item A: The content after the colon is an explanation of what they were unmistakable in front of.

Item B: unmistakable is a predicative position, so it cannot be an adverb.

Item C/D: Perfectly modifies the participle phrase formed little stone disks, apply the adverb form, and there is no symbol after perfectly.