Final answer:
The ALT hold mode can only be engaged at indicated airspeeds of 250 knots and above.
Step-by-step explanation:
The ALT hold mode can only be engaged at indicated airspeeds of 250 knots and above. ALT hold mode is a feature in aircraft autopilot systems that allows the aircraft to maintain a desired altitude automatically. When engaged, the autopilot system adjusts the aircraft's pitch and throttle to maintain the selected altitude.