Body composition is best described as a. the amount of lean muscle in a body b. the total amount of muscle in a body c. the total mass of fat in the abdomen d. the ratio of fat to other tissue in a body

The answer is D: the ratio of fat to other tissue in the body.
Body composition refers to the measurement of fat, muscle, bone and water in relation to each other. Muscle takes up less room in the body than fat does, so five pounds of muscle will take up less room than five lbs of fat. Body composition offers a way at accessing the state of health or fitness without depending solely on the measurement of weight.