Final answer:
The first step of the Adult Cardiac Chain of Survival is recognition of a cardiac emergency and activation of the emergency response system.
Step-by-step explanation:
The first step of the Adult Cardiac Chain of Survival is d. Recognition of a cardiac emergency and activation of the emergency response system. It is crucial to identify a cardiac emergency and call for help immediately. This step ensures that professional medical assistance will arrive as soon as possible to provide the necessary care.