A function of the mentalis muscle is to:

The mentalis muscle plays a critical role in facial expression, particularly in the area of the chin. When this muscle contracts, it causes the skin of the chin to wrinkle, which is often associated with expressions of doubt or displeasure. This muscle is situated at the tip of the chin and its primary function is indeed to create that wrinkling effect.

In contrast, the other functions mentioned in the options pertain to other muscles. Protruding the lower lip is primarily the function of the mentalis muscle as well, but the noteworthy point here is that the main observable action it is well-known for is the wrinkling of the chin. Elevating the eyebrows is mainly done by muscles like the frontalis, while closing the eyelids involves the orbicularis oculi muscle. Thus, the proper identification of the mentalis muscle's function focuses on its role in wrinkling the chin.