Final answer:
The most appropriate method for chest compressions during CPR on an adult is using the heel of one hand to compress the sternum 5 cm deep and at a rate of 100 compressions per minute, placed between the T4 and T9 lines.
Step-by-step explanation:
When performing chest compressions on an adult patient in cardiac arrest, the most appropriate method is using the heel of one hand to compress the sternum at least 2 inches (5 cm deep) at a rate of at least 100 compressions per minute. The hands should be placed between the lines at T4 and T9 of the patient's sternum. It's critical to avoid placing your hands too low to prevent driving the xiphoid process into the liver, which can be fatal.