You are attending to a responsive teenager injured after falling off the diving board stairs. What should you do?

Manually stabilizing the injured leg is the appropriate action because this technique helps prevent further injury while also providing support to the injured area. When an individual has sustained an injury, particularly to a limb, it's crucial to minimize movement to avoid exacerbating any potential damage, especially if there's a fracture or dislocation involved. By stabilizing the leg, it allows for blood flow to remain uninterrupted and reduces pain for the patient while waiting for further medical assistance.

The other options either pose a risk to the patient’s safety or do not address the immediate need for stabilization. For instance, snapping the bone ends back into place could cause further injury and should only be done by a medical professional. Simply tapping or squeezing the shoulder tests responsiveness but does not provide any support for the injury, and applying a pressure bandage around the entire length of the extremity could increase the risk of compromising circulation if not done correctly, especially if there is swelling or a fracture present. Therefore, stabilizing the leg is the most prudent and effective immediate response in this scenario.