The correct option is C,a refutation of a claim, with evidence.
Explanation:
Counterclaim is a claim made to weaken an earlier claim.
For instance, someone who encroaches on one's land can sue one at court of law in order to justify his ownership with fake documents believing that the person being used has no documents to the land.
A counterclaim in this sense would be that the genuine owner then sue the plaintiff in order to prove his right ownership to the land with legally recognized documents.