When he was finished with his bell work, Antione started working on his paper.

This sentence illustrates the following comma rule:

A. A comma is used to separate two or more adjectives modifying a noun
B. A comma is used after a dependent clause when the clause begins a sentence
C. A comma is used to set off an appositive from the rest of the sentence
D. A comma is used before a coordinating conjunction in a compound sentence