How long must the operator of each vessel engaged in a vessel-to-vessel oil transfer operation keep a signed copy of the declaration of inspection for?

Correct Answer: Option B — 1 month

33 CFR 156.150 requires that the Declaration of Inspection (DOI) be signed by the person in charge of both the vessel and the facility. The operator must maintain a copy of this signed document on board for a period of one month from the date of the transfer operation for inspection purposes.