Answer: The option that contains an appositive fragment is A. There's Jack. The most talented pianist I know.
Explanation: An appositive is a word or phrase which redefines or adds further information about a noun that is found right before or after it. Moreover, as an appositive does not express a complete thought, it cannot stand alone as a sentence. In that way, a sentence made up of only an appositive is called an appositive fragment, which, at the same time, is a sentence mistake. In option A., "The most talented pianist I know" is an appositive fragment because it is renaming the noun "Jack", but it is standing alone in the second sentence. This mistake can be corrected by writing "There's Jack, the most talented pianist I know".
