Question

Since he recorded his first hit,“Fingertips,” at the age of thirteen.

a.
Sentence
b.
Fragment

Answer 1

Thats a fragment, Good Luck!

Answer 2

This is meant to be a cause and effect statement, but there isn't an effect, there's only a cause.
Thus, this is a fragment.
B. Fragment

A fragment is something said that is not a complete sentence, meaning it's not a sentence.