What identifies the #1 end of a C car on PA5s?

The identification of the #1 end of a C car on PA5s can be attributed to the designated door numbers on the car. In this context, door numbers 1 and 7 play a pivotal role in marking the #1 end. This convention is typically adopted in rail and transit systems to establish a clear and consistent method for crew members and passengers to identify the front and rear of the train, which facilitates easier boarding, disembarking, and operational protocols.

While other options mention different identifiers or symbols, none of them conform to the standardized method of using door numbers for end identification. For example, door numbers 2 and 8 would indicate a different orientation or position on the vehicle, while references to fire alarms or windows do not establish a specific end in the same way. Thus, door numbers 1 and 7 are the recognized identifiers that directly signal the #1 end of a C car.