Before picking up five cars that are not a solid block of cars, what must be done?

The correct choice emphasizes the importance of safety and regulation adherence when dealing with railway operations, particularly regarding the handling and movement of train cars. According to the Class 1 Air Brake Test requirements, before coupling to five cars that are not a solid block, all five cars must be thoroughly inspected. This inspection ensures that the air brake systems are functioning properly, which is crucial for controlling the train and ensuring it can be safely operated.

The requirement for inspecting each car rather than just the rear car stems from the need to verify that each car is in good condition and equipped with functioning brakes. This proactive measure helps prevent potential incidents that could arise from mechanical failures or issues with the braking system during operation.

While visual checks on individual cars can be beneficial, relying solely on a visual inspection of just one car would not guarantee the overall safety and reliability of the train. Similarly, the idea that no inspection is required could compromise safety protocols established in the railway industry. Therefore, conducting a full inspection of all cars involved is not only a regulatory requirement but also a fundamental practice in maintaining safe rail operations.