When a vessel is swinging from side to side off course due to quartering seas, the vessel is __________.

Correct Answer: Option A — yawing

Yawing is the angular motion of a vessel about its vertical axis, causing the bow to swing from side to side. In quartering seas, the wave action exerts uneven pressure on the hull, pushing the stern and causing the vessel to deviate from its intended course, requiring constant rudder correction.