Under what condition can a brake be cut out?

The correct choice pertains to the operational procedures regarding train brakes. A brake should only be cut out if it is deemed defective. This is a critical safety measure, as cutting out a brake that is functioning well can lead to reduced stopping power and possible safety hazards during travel. The protocol ensures that only brakes that are not operational are removed from the system while those that are in good working condition remain functional.

In a situation where a brake is functioning properly, cutting it out could compromise the safety of the train, its crew, and its passengers. Routine observations and maintenance ensure that all parts of the train, especially braking systems, are in optimal condition. If a brake is determined to be defective based on inspection or performance during operations, it can then be safely cut out to ensure the integrity of the overall braking system.