Which of the following BEST defines "atrophy"?

structuresa.
b. Also known as "Achilles reflex," this test reveals the rate of contraction of the calf muscles and tendons when the Achilles tendon is struck; tests the neurologic reflexes that occur when the Achilles tendon is sharply struck by a physician during a physical examination
c. The decrease of mass in a muscle, organ, or other tissue, most often caused by changes in nutrition or disease c.
d. An abnormal tightening or shortening of muscles, usually in the extremities, that permanently limits the movement of the body part

C