Final answer:
Johann Sebastian Bach was not from the Classical period; he was a Baroque composer. Haydn and Mozart are key figures of the Classical era. Beethoven and Schubert composed during the Classical period, though they are also associated with the Romantic era, which followed.
Explanation:
The composer Johann Sebastian Bach was not from the Classical period; he was a Baroque composer, which predates the Classical period. Thus, the correct answer is C. Johann Sebastian Bach. The Classical period in music history spans from approximately 1750 to 1820 and its most renowned composers are Haydn and Mozart. Bach's music is characterized by intricate counterpoint and musical complexity typical of the Baroque era, which is earlier than the Classical era's emphasis on clarity, balance, and form.
Composers like Ludwig van Beethoven and Franz Schubert, while also associated with the Romantic era, began their careers within the Classical tradition. Beethoven, in particular, is recognized for bridging the gap between the Classical and Romantic periods with his later works reflecting the expressive style of the Romantic era. Franz Schubert is indeed most often associated with the Romantic era, but his early works are influenced by Classical forms and practices. Both Beethoven and Schubert are therefore often associated with the Classical period as well as the Romantic era.