Where should you place your hands when giving chest compressions?

To carry out a chest compression:

Place the heel of your hand on the breastbone at the center of the person's chest. Place your other hand on top of your first hand and interlock your fingers. Position yourself with your shoulders above your hands. Using your body weight (not just your arms), press straight down by 5 to 6cm (2 to 2.5 inches) on their chest. Keeping your hands on their chest, release the compression and allow the chest to return to its original position. Repeat these compressions at a rate of 100 to 120 times a minute until an ambulance arrives or you become exhausted.

The answer would be d. most contraceptives are effective when used properly

Yes, this is very true. specifically causing damage in the  dentrite.