In which situation would you most likely perform CPR?

Performing CPR is a critical intervention aimed at preserving life when someone's heart has stopped beating effectively or when their breathing has ceased. In this case, the correct answer highlights the necessity to respond to an individual who has stopped breathing.

When a person is not breathing, it indicates that oxygen is not being delivered to their vital organs, which can quickly lead to irreversible damage or death if not addressed. CPR combines chest compressions and rescue breaths to maintain blood circulation and oxygenation of the brain and other organs until emergency medical services can take over.

In contrast, during a seizure, an individual may have altered consciousness, but this does not necessarily mean they have stopped breathing or require CPR. Similarly, someone with a severe headache may be in pain, but this condition does not imply a life-threatening situation requiring CPR. An unconscious person who is breathing requires monitoring for airway and breathing support rather than CPR, as they are still receiving some oxygen. Thus, the situation of a person who has stopped breathing is the only scenario among the choices that directly calls for the immediate application of CPR.