All else being equal, why might a Master with a right-handed single-screw vessel prefer to berth port side to alongside rather than starboard side to, when both options are available?

A. Propeller handedness has no bearing on which side is preferable for berthing under any circumstances

B. Going astern to check the vessel's way on the final approach, the astern transverse thrust on a right-handed propeller pushes the stern to port — if berthing port side to, this tends to walk the stern in toward the berth, which can be used to advantage, whereas berthing starboard side to means the same effect would push the stern away from the berth, working against the approach

C. A right-handed propeller vessel can only ever berth port side to, with no alternative possible

D. The choice of berthing side is determined solely by which side the gangway is fitted, with no shiphandling consideration at all

A. The propeller blades on one side of the shaft work in deeper, less disturbed water than the blades on the other side, and this asymmetric loading, combined with the angle of the propeller race against the hull, produces a sideways force on the stern — for a right-handed propeller, this characteristically pushes the stern to starboard when going ahead and to port when going astern

B. It is caused entirely by wind acting on the superstructure, unrelated to the propeller

C. It is caused by rudder angle alone and disappears completely if the rudder is centred

D. It only occurs on twin-screw vessels and is not present on single-screw vessels

A. The difference is due only to engine RPM differences between ahead and astern settings

B. Going astern, there is no rudder effect to counteract the transverse thrust (since the rudder has little or no effect on a sternway-making vessel at low speed, especially with the engine going astern), so the sideways push of the propeller dominates the vessel's behaviour, whereas going ahead the rudder is normally effective and can counter or mask the transverse thrust

C. Transverse thrust does not exist when going astern under any circumstances

D. Transverse thrust is actually stronger when going ahead, not astern, and the question premise is reversed