According to U.S. regulations, what vessels are required to have the "Discharge of Oil Prohibited" placard?

Correct Answer: Option D — U.S. Vessels 26 feet or more in length

33 CFR 155.450 mandates that U.S. vessels 26 feet or more in length must display a durable 'Discharge of Oil Prohibited' placard. This requirement serves as a constant visual reminder to the crew regarding the legal prohibition against discharging oil into navigable waters, supporting compliance with the Federal Water Pollution Control Act.