Taurean, the tallest boy in class, reached the projector and turned it on.

This sentence illustrates the following comma rule:

A. Commas are used to set off a speaker’s exact words from the rest of the sentence
B. A comma is used to separate items in a series
C. A comma is used before a coordinating conjunction in a compound sentence
D. A comma is used to set off an appositive from the rest of the sentence