What prevents the wing of an aircraft from stalling at low subsonic speeds?

The correct choice is related to the concept of angle of attack, which is crucial in aerodynamics. Stalling occurs when the angle of attack exceeds a critical limit, causing airflow to separate from the wing's upper surface, resulting in a loss of lift. At low subsonic speeds, maintaining a small angle of attack is essential to ensure that the airflow remains attached to the wing, allowing the aircraft to generate sufficient lift without stalling.

In low-speed flight, pilots use techniques such as keeping the angle of attack within safe limits to prevent reaching that critical angle. This is particularly important during phases of flight like takeoff and landing.

Other factors, such as airspeed, weight, and attitude, can influence stall characteristics, but controlling the angle of attack directly relates to preventing stalls. By keeping the angle of attack small, the aircraft can sustain lift and avoid entering a stall, which is why this choice is the most relevant in the context of the question.