How long must equipment be observed for movement when testing the effectiveness of applied hand brakes?

The correct choice indicates that equipment must be observed for movement for a duration of 1 minute when testing the effectiveness of applied hand brakes. This time frame allows sufficient observation to ensure that the brakes are properly holding the equipment in place without any noticeable movement. By monitoring for a full minute, you can effectively verify the reliability of the hand brakes under typical conditions, ensuring they are functioning as intended before proceeding with any operations. Brief observations may not provide a reliable assessment of brake effectiveness, and this duration strikes a balanced approach to safety and practicality in the railway industry.