What is exercise? select one: a. muscular activity of vital organs, especially the intestine, heart, and lungs. b. caloric expenditure that results from contracting skeletal muscles. c. skeletal muscle contractions that are planned and conducted to increase muscle mass d. movement that results from any muscular contraction?

c. skeletal muscle contractions that are planned and conducted to increase muscle mass
Skeletal muscle contraction is one immediate effect of exercise on the muscular system.  Other effects include higher blood flow to muscles and increased muscle temperature, Regular exercise increases bone width and density, strengthens muscles, tendons, and ligaments. It also increases flexibility at joints. Exercise  also leads to bigger muscles,  improved muscle endurance, and more stable joints

B. to increase the amount of antibiotics in the body