What must the HRST Master perform before sending a rappel lane?

The correct answer highlights the importance of safety and preparedness in high-risk activities like rappelling. Performing a final check and ensuring a belay man is present are critical steps that ensure not only the safety of the person rappelling but also the efficiency of the operation. The final check serves to confirm that all gear is properly secured, safety measures are in place, and that communication lines are clear. The presence of a belay man adds an additional layer of safety, providing a backup in case the person rappelling encounters any difficulties.

In this context, safety is paramount, and each action taken prior to sending someone down the rappel lane is designed to minimize risks. Other steps, although significant, do not directly focus on immediate safety in the same crucial manner as verifying all equipment and support personnel.