Which of the following is a sign of cardiac arrest?

The identification of cardiac arrest is crucial for timely and effective intervention. The most definitive sign of cardiac arrest is when a person is unresponsive and not breathing. In this state, the heart has stopped functioning effectively, leading to a lack of circulation and oxygenation to the brain and other vital organs. This condition requires immediate action, such as calling emergency services and starting cardiopulmonary resuscitation (CPR).

In contrast, the other signs listed suggest different medical scenarios. A responsive but confused individual may exhibit signs of a transient ischemic attack or other conditions, but they are not indicative of cardiac arrest. A person who is pale yet breathing normally may be experiencing shock or another issue, but they are not in cardiac arrest. Finally, someone who is awake but experiencing chest pain has a different set of concerns, possibly indicating a heart attack or other cardiac issues, but again is not unresponsive and not breathing, which signifies cardiac arrest.