A vessel is equipped with a single right-handed screw. With rudder amidships and calm wind，the vessel will most likely back（）.

A.at anchor
B.mine-clearing
C.engaged in fishing
D.engaged in towing

A.turning maneuver
B.course setting
C.position fixing
D.regulating speed

A.permits the rudder to move faster
B.generates more power
C.can turn without using her rudder
D.can suck the water away from the rudder