Final answer:
A mutilated security is considered a good delivery when validated by the transfer agent, who is responsible for ensuring that securities are in an acceptable condition for transfer.
Step-by-step explanation:
A mutilated security is considered a good delivery if validated by the D. Transfer agent. The transfer agent is responsible for verifying and guaranteeing the authenticity of a security, especially if it has been damaged or is in a less-than-perfect condition. Other entities, such as the issuer, the contra-broker, or the customer, do not have the authority to validate a security as a good delivery. The transfer agent acts as an intermediary to ensure that the securities are appropriately endorsed and are in a form that is acceptable to be transferred from the seller to the buyer.