INTERNATIONAL ONLY Which vessel is required to sound two prolonged blasts followed by one short blast on the whistle?

Correct Answer: Option B — An overtaking vessel in a narrow channel

Rule 34(c)(i) of the COLREGS (International Rules) requires that a vessel overtaking another in a narrow channel must signal her intention by sounding two prolonged blasts followed by one short blast. This indicates the intent to pass on the starboard side of the vessel being overtaken.