Which part of the skull provides protection for the brain?

The cranial cavity is the correct choice because it houses and protects the brain from external impacts and injuries. This protective feature is attributed to the bony structure that forms the skull, which includes several bones that create a rigid encasement around the brain. The cranial cavity not only shields the brain physically but also provides a stable environment that helps maintain intracranial pressure and supports the brain's structures and functions.

On the other hand, components like the facial skeleton, mandible, and nasal cavity serve various functions but are not primarily responsible for brain protection. The facial skeleton contributes to the structure and appearance of the face, while the mandible acts as the lower jaw essential for mastication. The nasal cavity is involved in respiratory functions, such as air passage and filtration, but does not provide protective coverage for the brain itself. Thus, the cranial cavity is uniquely designed for safeguarding the brain, making it the correct answer to this question.