After an inspection, how long must brakes remain applied during re-testing if they release prematurely?

The correct choice specifies that the brakes must remain applied for at least 3 minutes during re-testing if they release prematurely. This duration ensures a thorough assessment of the brake system's functionality.

By keeping the brakes applied for this extended period, it allows for any potential leaks or issues to become apparent, ensuring safety and reliability. The 3-minute timeframe is established to provide enough time for internal mechanisms to stabilize and demonstrate consistent performance. This practice is integral to safe rail operations, as it helps identify and confirm that the brake system functions as intended before resuming service.

Other options may suggest different timeframes, which do not meet the necessary standards for safety and reliability in testing brake functionality, highlighting the importance of the specified duration in maintaining operational integrity.