Final answer:
Physiology is the branch of biology that studies the normal functions of living organisms, focusing on the body's structures and their interactions to support life.
Step-by-step explanation:
The answer is OA. It deals with the normal functions of living organisms.
Physiology is the study of the normal functions of living organisms. It is a branch of biology, not physics. It does not focus only on how elite athletes can improve physical performance, although it does include the study of human performance. It also concentrates on the interior of the body, including the effects of nutrition and medication.
The other options are all false. Physiology is not classified as a branch of physics. It does not focus only on how elite athletes can improve physical performance. And it does not concentrate only on the exterior of the body.