What type of propeller consists of a flat disc set flush with the under surface of the vessel's hull with a number of vertical, rudder like blades projecting from it?

Correct Answer: Option D — Cycloidal propeller

Cycloidal propellers, such as the Voith Schneider design, utilize a rotating disc flush with the hull. Vertical blades oscillate to provide omnidirectional thrust. This system eliminates the need for a conventional rudder, providing exceptional maneuverability for tugs and specialized offshore support vessels.