【单选题】

A large vessel is equipped with a controllable pitch propeller. Which statement is TRUE?（）.

A . When dead in the water，it is often difficult to find the neutral position and slight headway or sternway may result
B . When going directly from full ahead to full astern，there is complete steering control
C . When the vessel has headway and the propeller is in neutral，there is no effect on rudder control
D . When maneuvering in port，full ahead or astern power can usually be obtained without changing shaft RPM