Prior to engine shutdown, both pilots must ensure seats are in what position?

The correct choice regarding the position of seats prior to engine shutdown is that both pilots must ensure their seats are in a full up position. This is important for several reasons related to safety and emergency preparedness.

Having the seats in the full up position allows for optimal visibility and access to the instruments, ensuring that pilots can effectively monitor the aircraft's systems and surroundings until the very end of the flight. Additionally, in the event of an emergency evacuation, a full up seat position facilitates quicker egress from the cockpit. It minimizes the risk of being hindered by seat adjustments that might delay or complicate the pilots' exit.

While the other options may have their own contexts or situations where they are appropriate, they do not align with the pre-shutdown protocols that prioritize readiness and safety in aviation procedures. The full up position thus serves crucial operational and safety functions right up until engine shutdown.