All of the following methods are ways to correct a run-on sentence except what? a. putting a comma in between the complete sentences.
b. inserting a period between the complete sentences.
c. placing a semicolon between the complete sentences.
d. adding a conjunction between the complete sentences.

You don't want to put a comma between the complete sentences, because that just prolongs the sentences, rather than correcting it. You can do B no matter what. If the sentences are in relation to each other, then you can add a semicolon. For example, he liked the dog; it had soft and silky ears. If the first sentence is dependent on the other sentences, then add a conjunction. For example, He had to go to the store because he needed eggs.