Question 156General Subjects - 1st Asst/Chief

The correct answer is B) Cycloidal propeller. A cycloidal 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. This design allows the thrust vector to be varied in both magnitude and direction, providing excellent maneuverability. This is the defining characteristic of a cycloidal propeller that distinguishes it from other propeller types like helicoidal, contra-rotating, or tandem propellers. The other answer choices are incorrect because they do not accurately describe the specific features of a cycloidal propeller as outlined in the question.