Which of the following accurately describes the way in which a muscle moves?
a. No ATP is needed in the contraction of a muscle.
b. When actin filaments are pulled toward the center of the sarcomere, the fiber shortens.
c. During contraction, cross-bridges pull the myosin to the center of the sarcomere.
d. Interaction and attachment between myosin and actin cause a muscle fiber to relax.