Which of the following factors can affect an aircraft's stall speed?

The correct answer highlights the significant influence of aircraft weight and configuration on stall speed. Stall speed is defined as the minimum airspeed at which the aircraft can maintain level flight. As weight increases, the stall speed also increases because a heavier aircraft requires more lift to counteract the additional weight. The configuration of the aircraft, such as the position of the flaps or landing gear, also plays a crucial role. For example, extending flaps increases lift at lower speeds which can decrease stall speed. Conversely, retracting flaps or landing gear generally increases stall speed because the aircraft requires a higher speed to generate the necessary lift.

While factors such as aircraft color or paint type do not influence aerodynamics or stall speeds, they may have aesthetic or minor performance implications, but these are not relevant to stall speed dynamics. Similarly, while the experience and skill of the flight crew are critical for overall safety and operational effectiveness, they do not intrinsically change the aerodynamic characteristics of the aircraft that determine stall speed. Lastly, aircraft age and maintenance history affect reliability and performance but do not directly influence stall speed calculations in the context of weight and configuration. Thus, the factors that most directly alter stall speed are indeed aircraft weight and configuration.