What triggers the stick pusher in the stall warning system?

The stick pusher in the stall warning system is activated by a high angle of attack with no action from the pilot. This mechanism is designed as a safety feature to help prevent an aerodynamic stall, which occurs when the aircraft's wings are at an angle of attack that exceeds their critical limit. When the system detects that the aircraft is approaching this critical angle of attack, the stick pusher automatically pushes forward on the control yoke to reduce the angle and help the pilot regain control of the aircraft.

In contrast, the other options do not directly trigger the stick pusher. For example, flap position at zero degrees does not inherently indicate an impending stall, as stall conditions can occur at various flap settings. Low airspeed with high thrust settings does not automatically trigger a stick pusher activation; instead, it’s the angle of attack that's critically monitored. Lastly, pilot disengaging the autopilot is related to the control of the aircraft but does not specifically initiate a stall warning or activate the stick pusher. Thus, the correct answer focuses on the critical factor of the angle of attack and the absence of corrective action from the pilot.