What must you do if you have a loaded rifle after the command STOP is given?

When the command STOP is given, it indicates that all activities with the rifle should cease immediately, and safety protocols must be followed. Opening the action of the rifle serves as a critical safety measure. This action ensures that the chamber is visible and checks that no pellet is in the firing position, thereby preventing any accidental discharge.

By opening the action and waiting for further instructions, you demonstrate responsibility and adherence to safety protocols, which are essential in ensuring the safety of everyone present. This step allows instructors or peers to assess the situation before further actions are taken, which is vital for maintaining a safe environment during training. It's important to wait for additional guidance to ensure all safety procedures are properly followed.

The other options do not adequately prioritize safety or compliance with the STOP command, making them less appropriate in this context.