What is the main function of the crew alerting system in a Cabin Atmosphere Control System (CACS)?

The main function of the crew alerting system in a Cabin Atmosphere Control System (CACS) is to inform the crew of anomalies in the cabin atmosphere. This system is crucial for maintaining the safety and comfort of both passengers and crew during flight. If any issues arise, such as a drop in cabin pressure, a malfunction in the air conditioning system, or an unsafe level of cabin contaminants, the alerting system promptly notifies the crew. This allows them to take appropriate actions to address the situation, ensuring that the environment remains safe, which is vital for the overall operation of the aircraft.

In contrast, monitoring passenger comfort levels, regulating cabin lighting, and controlling the in-flight entertainment system, while relevant to the overall passenger experience, do not directly tie into the primary safety responsibilities of the crew alerting system. The crew alerting system is specifically designed for safety-critical alerts regarding the atmospheric conditions in the cabin, making option B the correct choice.