Final answer:
The covenant that protects against third-party claims in a property transaction is known as the covenant of seisin.
Step-by-step explanation:
The covenant that warrants against claims of third parties is C) seisin. A covenant of seisin assures that the grantor owns the property and has the legal right to convey it, which guarantees the grantee that no third parties have undisclosed interests in the property. This covenant is one aspect of a general warranty deed, and it helps to protect the buyer's interests by ensuring that they are receiving clear title to the property. The concept of seisin involves the legal possession of property, which would be encumbered if there were claims by other parties.