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 B — Cycloidal propeller

A cycloidal propeller, such as the Voith Schneider, features vertical blades mounted on a rotating disc flush with the hull. By varying the pitch of individual blades during rotation, the unit can produce thrust in any direction, providing exceptional maneuverability without the need for a conventional rudder.