What is the primary function of a propeller in an aircraft?

The primary function of a propeller in an aircraft is to create thrust for forward motion. This is accomplished by the propeller blades spinning around their hub, which generates a difference in air pressure between the front and back of the blades. The higher pressure at the rear pushes the aircraft forward. This thrust is essential for overcoming drag and enabling the aircraft to accelerate and maintain cruise speeds during flight.

The other options focus on aspects related to aircraft performance but do not accurately describe the primary function of a propeller. For instance, lift is primarily generated by the wings of an aircraft, not by the propeller. While stabilization and altitude control are vital for overall flight dynamics, these functions are typically managed by control surfaces like ailerons, rudders, and elevators, along with the aircraft's design, rather than directly through the propeller’s action.