Final answer:
The agonist, or prime mover, is responsible for producing specific movements, with assistance from synergists which can also act as fixators to stabilize the bone at the muscle's origin. Antagonists perform the opposing action to the agonists(C).
Step-by-step explanation:
The functional group with the major responsibility for producing a specific movement is known as the agonist(C), which is also referred to as the prime mover. The agonist is the principal muscle involved in an action. For example, the biceps brachii serves as the agonist when lifting a cup. Other muscles such as the brachialis may assist the prime mover and are known as synergists. A synergist can also act as a fixator by stabilizing the bone that serves as the attachment point for the prime mover's origin.
Antagonists are muscles that perform the opposite action to the agonists. They play a crucial role in maintaining body position and controlling the speed of movements. Essentially, while the agonist acts to move, the antagonist works to slow down or stop the movement.