What is the correct command to ensure accountability of team members at the start of a rescue operation?

The command "Roll call" is essential for ensuring accountability of all team members at the start of a rescue operation. Conducting a roll call allows the team leader to confirm that everyone is present and accounted for before the operation begins. This step is critical for the safety and coordination of the rescue team, as it helps to identify any missing personnel and ensures that all members are aware of their roles and responsibilities.

In contrast, the other commands listed—such as "Belay ready?", "Main line ready?", and "Edge tender ready?"—focus more on specific equipment or operational readiness rather than on the accountability of individuals within the team. While these commands are important for safety and operational protocols during a rescue, they do not serve the primary purpose of confirming the presence and readiness of team members. Hence, "Roll call" stands out as the most effective command for establishing accountability at the outset of a rescue.