What factors determine an aircraft’s stall speed?

The stall speed of an aircraft is influenced primarily by its weight, configuration, and aerodynamic design. When considering weight, an increase in the aircraft's load requires a higher angle of attack to maintain level flight, ultimately raising the stall speed. Similarly, the aircraft's configuration—such as whether flaps are extended or retracted—affects its aerodynamic performance and, therefore, its stall speed. For instance, deploying flaps can lower the stall speed because it changes the lift characteristics at lower speeds. The aircraft's aerodynamic design, including the wing shape and airfoil characteristics, also plays a significant role; different designs will behave differently as they approach the critical angle of attack.

While the pilot's experience and control inputs are significant for overall flight safety and handling, they do not intrinsically change the aircraft's stall speed itself. Factors like altitude and weather can influence performance, but they do not directly determine the stall speed under standard conditions. Thus, the correct choice emphasizes the inherent characteristics of the aircraft and how they define the point at which the aircraft can no longer maintain controlled flight.