The correct answer is D) Lower half of the sternum. During CPR, chest compressions should be applied to the lower half of the sternum, which is the bony structure in the center of the chest. This ensures that the compressions are being delivered directly over the heart, allowing for effective blood circulation. Applying pressure to the lower half of the sternum is the recommended technique as it avoids potential injury to the upper chest area. The other options are incorrect because: A) Applying pressure to the top half of the sternum would not be effective for CPR; B) Targeting the left chest over the heart is not the proper technique; and C) Applying pressure to the tip of the sternum could cause injury.