The correct answer is D) approval of the Commandant. According to the regulations governing the issuance of merchant mariner credentials, a mariner whose credential has been revoked cannot be issued a new credential without the approval of the Commandant of the U.S. Coast Guard. This requirement is in place to ensure that the Commandant, as the head of the Coast Guard, has oversight and control over the reinstatement of revoked credentials. The other options are incorrect because they do not align with the regulatory requirements. The Officer-in-Charge, Marine Inspection, and an administrative law judge do not have the authority to approve the issuance of a new credential after a revocation. Additionally, simply taking a new examination is not sufficient, as the Commandant's approval is still required.