Cranial nerves are the nerves that originate from the brain and control various functions of the head and neck. There are 12 pairs of cranial nerves, each with its own specific functions.

Mixed Nerves:
Mixed nerves are nerves that contain both sensory and motor fibers. In other words, they carry both sensory information from the body to the brain and motor commands from the brain to the body.

Out of the 12 pairs of cranial nerves, only some are considered mixed nerves.

The following cranial nerves are mixed nerves:

1. Trigeminal Nerve (CN V): This nerve is responsible for sensory information from the face, as well as motor control of the muscles involved in chewing.

2. Facial Nerve (CN VII): The facial nerve controls the muscles of facial expression and also carries sensory information from taste buds on the anterior two-thirds of the tongue.

3. Glossopharyngeal Nerve (CN IX): This nerve receives sensory information from the posterior one-third of the tongue, and it also controls some muscles involved in swallowing.

4. Vagus Nerve (CN X): The vagus nerve is involved in various functions, including control of the heart, lungs, and digestive system. It carries both sensory and motor fibers.

Out of the 12 pairs of cranial nerves, these four pairs (CN V, CN VII, CN IX, and CN X) are considered mixed nerves as they contain both sensory and motor fibers. Therefore, the correct answer is option C, which states that there are four pairs of cranial nerves that are mixed nerves.