The correct answer is D) starboard until headway is lost and then to port. When a single-screw vessel (with a right-hand propeller) goes full ahead with good headway and the engine is put astern with the rudder hard left, the stern of the vessel will initially swing to starboard. This is due to the propeller's rotation, which creates a sideways force on the stern, pushing it to starboard. As the headway is lost, the vessel will then swing to port, as the rudder's effect becomes more pronounced. The other options are incorrect because A) the stern will not swing to port initially, B) the swing to port will not be slow at first, and C) the stern will not just swing to port without first swinging to starboard.