Read the following sentence and answer the question. “The hunter shot the arrow, it killed a deer.”

Which of the following best explains why the comma is incorrectly used in the sentence above?

A comma cannot be used to join two dependent clauses.
No explanation is needed; the comma is used correctly.
A comma cannot join two independent clauses unless it is followed by a coordinating conjunction.
A period is the only correct punctuation to use after the word "arrow."