Final answer:
The temporalis muscle elevates and retracts the mandible, assisting in the upward movement to close the mouth and pulling the lower jaw backward.
Step-by-step explanation:
The temporalis muscle is one of the muscles responsible for mastication, or chewing. According to the information provided, the temporalis muscle assists in elevating the mandible, which is the upward movement necessary for closing the mouth. It also retracts the mandible, meaning it pulls the lower jaw backward. Therefore, the correct description of the action of the temporalis muscle is that it elevates and retracts the mandible. You can feel the temporalis muscle engage by placing your fingers on your temple while chewing, which will allow you to feel the muscle activate as it works in conjunction with the masseter muscle, the main muscle used for chewing.