The sentence in which the adverb clause modifies an adjective is the second one - The veteran appeared proud as he saluted the flag. The adjective here is <em>proud</em>, and the adverbial clause is <em>as he saluted the flag. </em>As you can see here, that clause is describing the adjective in more detail. When did the veteran appear proud? - As he saluted the flag (it obviously modifies the word <em>proud</em>)
