Final answer:
When muscles are exposed to heat, they contract and pull away from the source to prevent injury, making c) Muscles contract and pull away from the fire the correct answer. In muscle action such as flexion, the biceps contract while the triceps relax, demonstrating muscle pairs' cooperative function to facilitate movement.
Step-by-step explanation:
During fire direction, muscles respond to heat by undergoing a reflex contraction. This response is an effort to move the body part away from the source of heat, a protective mechanism to prevent injury. Therefore, the correct answer to what happens to muscles during Fire Direction, where they contract and pull away from the fire, is c) Muscles contract and pull away from the fire. This muscular response is critical for preventing burns and damage to the tissue.
Relating to the action of muscles in general, such as flexion and extension, where pairs of muscles like the biceps and triceps work in opposition to bend and straighten the arm respectively, is an example of how muscles contribute to movement. When the biceps contract, the arm bends at the elbow because the angle between bones is decreased, which corresponds to option b in the question about flexion. Conversely, when the triceps contract, they straighten the arm and the biceps muscle relaxes and elongates.