BOTH INTERNATIONAL & INLAND You are heading due east (090°) and observe a vessel's red sidelight on your port beam. The vessel may be heading __________.

Correct Answer: Option C — southwest (225°)

Using relative bearings and geographic plotting, a vessel heading due east (090°) with another vessel's red sidelight on its port beam means the target vessel must be heading southwest (225°), crossing from port to starboard within the red sector.