Smooth muscles are located in visceral organs of the body. For example, urinary bladder, uterus, respiratory tract, etc. These muscles are not connected to bones and do not function in the movement like walking and running. In contrast, skeletal muscles attach directly to the skeleton which synchronizes the movement of muscles with bones. These skeletal muscles are attached to bones with a tough, flexible band of fibrous connective tissue called as, tendon. When the skeletal muscles contract, it pulls the tendon attached to the bone, aiding to the movement of bones. Thus the answer is D 'Skeletal muscles contract and pull the tendon to move the bones.'