A) Correct. CPR is a life-saving technique used to restore circulation and maintain oxygenation in individuals who have experienced cardiac arrest or have stopped breathing. It involves chest compressions to manually pump blood and provide oxygen to vital organs.

B) Incorrect. CPR is not intended to stop all heart rhythms; rather, it aims to keep blood flowing to vital organs until more advanced medical assistance can be provided.

C) Incorrect. CPR is a critical intervention for severe emergencies like cardiac arrest and is not limited to treating minor heart conditions.

D) Incorrect. While CPR is crucial in the immediate response to cardiac arrest, it is not a substitute for professional medical care. Timely activation of emergency medical services is essential to ensure the best possible outcome.