Parallel structure is the repetition of a grammatical pattern.
Romeo Montague is the embodiment of...
- romantic idealism, passionate intensity, and adolescent rebellion. Extract the core words to get "idealism, intensity, rebellion". This list follows the pattern "noun, noun, noun".
- romance, passionately intense and raging with adolescent rebellion. Extract the core words to get "romance, intense, raging". This list follows the pattern "noun, adjective, verb".
- romantic idealism, passionate, intensity, and adolescent rebelling. Extract the core words to get "idealism, passionate, intensity, rebelling". This list follows the pattern "noun, adjective, noun, verb".
- romance and idealism - passionate, intense, an adolescent rebel. Extract the core words to get "passionate, intense, a rebel". This follows the pattern "adjective, adjective, noun".
Only the first choice repeats a grammatical pattern. Therefore the correct answer is Choice A.