Pressing the ALT button on the FCP will:

• A. Provide instantaneous capture of the pressure altitude existing in the FCC at the time of engagement
• B. Arm the altitude hold mode automatically
• C. Reset the altitude to zero
• D. Disable the altitude alert

Answer: (A)

The ALT button is used to capture the aircraft’s current pressure altitude and store it in the flight control computer as the target altitude. This gives you a precise reference to hold when you engage altitude-related modes. It’s not an automatic arm for altitude hold, it doesn’t reset altitude to zero, and it doesn’t disable altitude alerts.