Final answer:
You should attempt defibrillation with the AED when it recommends a shock for the 12-year-old child who has collapsed and is unresponsive, after making sure everyone is clear of the child.
Step-by-step explanation:
If a 12-year-old child has suddenly collapsed on the playground, is unresponsive, apneic, and pulseless, and CPR (cardiopulmonary resuscitation) is in progress when an AED (Automated External Defibrillator) is ready to be used and recommends a shock, the next step should be to attempt defibrillation. This involves making sure everyone is clear of the child and then pressing the button to deliver the shock as the AED instructs. Once the shock is administered, continue following the AED prompts, which will usually instruct you to resume CPR until the device re-analyzes or emergency medical services arrive. Defibrillation is necessary to try and restore a normal heart rhythm and improve the chances of survival.