What is blood pressure?

• A. It is the pressure that the blood clot exerts over the brain.
• B. It is the pressure that blood receives on account of faulty commands from the brain
• C. It is the pressure that fatness or old age exerts on the body's circulatory system.
• D. It is the amount of pressure on the blood as a result of the heart's pumping function and the resistance of the arterial walls.