What cabin pressure value triggers the red CAS indicator?

The red CAS (Crew Alerting System) indicator is designed to alert the flight crew of potential issues regarding cabin pressure. The value that triggers this warning is crucial for maintaining safe cabin altitude and pressure conditions.

In this case, the correct cabin pressure value that activates the red CAS indicator is 6.35 psi or -0.25 psi. These specific thresholds are established based on safety regulations and aircraft design to ensure that the cabin remains pressurized within safe operational limits. Exceeding or falling below these values can lead to uncomfortable or dangerous conditions for passengers and crew, necessitating immediate awareness and action from the flight crew.

Understanding the correct thresholds helps in recognizing the operational limitations and ensuring that the aircraft's pressurization system functions correctly. The other options represent values that would not appropriately trigger the indication system for cabin pressure alerts, thus making option B the critical value for maintaining safety in flight operations.