What is the maximum pressure altitude below which spins are prohibited?

The correct answer is based on safety regulations concerning spin recovery and the aircraft's performance characteristics. In the T-6A, spins are prohibited below a maximum pressure altitude of 10,000 feet because the increased density altitude can adversely affect the aircraft's performance during recovery from a spin. At lower altitudes, the aircraft may not have sufficient airspeed or altitude to recover safely, which could lead to a dangerous situation if a spin does occur. This regulation ensures that pilots operate the aircraft within parameters that allow for effective recovery techniques.

The other altitude options represent heights where spins may be performed; however, operating below 10,000 feet heightens the risk associated with spin recovery due to the environmental factors involved. Factors such as increased ground proximity and reduced time for recovery maneuvers place constraints on the pilot's ability to manage the aircraft effectively, hence the prohibition at this altitude.