You are signing on a crew. A man presents a Merchant Mariner's Document that you suspect has been tampered with. Which action should you take?

Correct Answer: Option B — Refuse to sign the man on articles until authorized by the Coast Guard.

If a Merchant Mariner Credential appears tampered with, the Master must exercise due diligence. Under 46 CFR 15.401, the Master is responsible for verifying the validity of credentials. Refusing to sign the individual until the Coast Guard verifies the document prevents the employment of unqualified or fraudulent personnel.