Which device is mentioned to be installed on both seats during an emergency ground egress?

The correct response refers to the seat safety pin, which is essential for securing the seat in place, especially during emergency ground egress. This device ensures that the pilot and co-pilot's seats can be safely locked in position until it is necessary to release them during an emergency situation. In the context of egress procedures, having the seat safety pin installed on both seats provides an added layer of safety and prevents unexpected movements that could hinder swift evacuation.

Other options, like the canopy safety pin, shoulder strap, and lap belt, serve different purposes. The canopy safety pin is particular to securing the canopy and not relevant to seat stability during egress. Similarly, while shoulder straps and lap belts are critical for occupant safety during normal operations, they do not play a role in the specific context of securing seats for emergency ground egress. Hence, the inclusion of the seat safety pin is the appropriate choice for this scenario.