What systems work in conjunction with the CACS to provide emergency oxygen?

The correct choice identifies the systems that directly interact with the Cabin Atmosphere Control System (CACS) to ensure that adequate emergency oxygen is available during critical situations, such as cabin depressurization.

Emergency oxygen systems are specifically designed to deploy oxygen masks when the cabin pressure falls below a safe threshold. These systems can deliver oxygen both to the crew and to passengers, allowing passengers to breathe normally until the aircraft is brought back to a safe altitude or the situation is resolved. The integration of these systems with the CACS is crucial because the CACS manages overall cabin atmosphere, including maintaining pressure and controlling air quality, which in turn affects the deployment and functionality of the emergency oxygen supply.

Passenger masks are part of this emergency oxygen provision; they are activated in an emergency situation and are designed to provide passengers with breathable oxygen. Without the effective functioning of both the emergency oxygen systems and the passenger masks, the overall goal of ensuring passenger safety and comfort during emergencies would be severely compromised. The coordination between these systems is vital for a well-functioning emergency response in the cabin.