Two related independent clauses can be joined by a

a) comma

b) comma splice

c) semicolon

d) run-on

c) Semicolon

Explanation:

When the content of two or more independent clauses are closely related, we can join them with a semicolon or coordinating conjunction like "or," "and," "but," "yet" or "so." If we used a comma instead, a comma splice would occur, which is one of the mistakes made when using a comma incorrectly.

Likewise, a "run-on" is not a possible answer either because it refers to a sentence-error that occurs when two independent clauses are not joined correctly.