How long is a credential issued by the U.S. Coast Guard for Master of Towing Vessels valid for?

Correct Answer: Option C — 5 years and must be renewed

46 CFR 10.227 establishes that all Merchant Mariner Credentials (MMC), including those for Master of Towing Vessels, are issued for a five-year validity period. Mariners must meet specific service and physical requirements to renew their credentials before the expiration date to maintain their professional standing.