I believe the answer is C) frightened. A participle is a word formed from a verb, and used an an adjective or a noun. Since frightened and climbed are both verbs, that narrows it down to either C or D. From there, frightened is an adjective, while climbed is nor an adjective or a verb.
D. Since the t in the is not capitalized, the sentence before it should end with a comma inside the punctuation marks
As an aging, conventional person of little consequence
