The main clue in this question is the word “though,” which sets up an opposite relationship between how Peter “did not appear to be particularly” and what he actually was. The missing words describe what he did not appear to be and what he actually was, so they must be synonyms in order to maintain the opposite relationship. Brawny means strong and muscular, while strongest means having the most power and ability to move heavy objects. These words have similar meanings, so choice (A) is correct.
