What is the minimum altitude for autopilot use with an inoperative radio altimeter during approach?

The minimum altitude for autopilot use with an inoperative radio altimeter during approach is 160 feet. This altitude is critical because it ensures that pilots maintain adequate altitude awareness during the approach phase, especially when relying on other instruments instead of the radio altimeter. The radio altimeter provides precise altitude information above ground level, which is vital for maintaining safe flight parameters during the final stages of landing. When it is inoperative, the autopilot can still be utilized safely up to 160 feet, allowing for a standard margin that accommodates any potential errors in vertical speed or altitude reading from other instruments.

Higher minimum altitudes listed in other options would not align with the operational limits provided for managing the aircraft safely in such scenarios.