What function does a propeller serve in an aircraft?

A propeller primarily functions to create thrust for the aircraft, which is essential for overcoming drag and enabling forward motion. When the blades of the propeller rotate, they push air backward, generating a reaction force that propels the aircraft forward according to Newton's third law of motion. This thrust allows the aircraft to accelerate, climb, and maintain cruising speeds during flight.

While the other options reference important aspects of aircraft performance and maneuverability, they do not accurately describe the primary role of a propeller. For instance, lift is generated by the wings due to their shape and angle of attack rather than by the propeller itself. Similarly, stability is primarily a function of the aircraft’s design and control surfaces rather than the propeller, which does not stabilize the aircraft but rather provides forward motion. Enhancing aerodynamic efficiency might indirectly relate to the propeller’s design or operation but is not its main function. The propeller's key role remains in providing the necessary thrust for flight.