The answer is C. An appositive phrase is where a noun is restated. "A town in Florida" is right next to the noun, St. Augustine. C. restates the noun in a different way, right next to the noun, St. Augustine.
An appositve phrase is a noun or noun phrase that renames or explain another noun which is located right next to the appositive phrase.
The apposive phrase should be between commas. In this case, the phrase "a town in Florida" is explaining or renaming the noun "St. Augustine" and is placed between commas.
