Final answer:
Among the given composers, Mozart is the one from the 'classical' period, with Beethoven spanning both Classical and Romantic periods, Bach from the Baroque era, and Verdi from the Romantic era.
Step-by-step explanation:
The composer from the 'classical' period among the options provided is Mozart. The Classical period in Western music is generally considered to have lasted from the mid-18th to the early 19th centuries, and Wolfgang Amadeus Mozart along with Joseph Haydn are two of the most celebrated composers from this era.
While Beethoven began his career within the Classical period, his later works greatly contributed to the advent of the Romantic era, which valued emotional expression and individuality in music. Johann Sebastian Bach is associated with the Baroque era, which predates the Classical period, and Giuseppe Verdi composed during the Romantic era, making him not a representative of the Classical period.