A nurse is teaching a class about skeletal muscles. Which of the following should the nurse identify as a function of skeletal muscles?

A. Skeletal muscles are voluntary muscles attached to bones that enable movement of the body, including fine motor actions such as forming a fist or grasping objects. They are under conscious control and work by contracting and pulling on bones to produce movement. B. The bronchioles are composed of smooth muscle, not skeletal muscle. Smooth muscle in the respiratory tract contracts or relaxes involuntarily to regulate airflow, not under voluntary control. C. The bladder is lined with smooth muscle (detrusor muscle), which contracts involuntarily to expel urine. Skeletal muscles do assist in controlling the external urethral sphincter, but the bladder contraction itself is smooth muscle activity. D. The heart is made of cardiac muscle, which contracts involuntarily to pump blood. Cardiac muscle is striated like skeletal muscle but functions automatically, independent of conscious control.