What is critical to check before the emergency oxygen assembly is activated?

The correct choice emphasizes the importance of checking the pressure in the oxygen assembly before activating the emergency oxygen system. This is crucial because the pressure directly impacts the availability of oxygen. If the pressure is too low, it may not provide the necessary flow of oxygen required for effective breathing, especially in an emergency situation. Ensuring that there is adequate pressure helps confirm that the system is ready to function properly when needed.

While other factors play a role in the overall functionality of the emergency oxygen assembly, such as the integrity of connections and the functionality of components, their impact is secondary to ensuring sufficient pressure. Without proper pressure in the oxygen assembly, even a well-connected or functional system may not deliver the oxygen needed for survival in an emergency. Thus, checking the pressure acts as a primary indicator of the system's readiness.