The protruding bone below the crest area at the back of the head is the...

The correct option is the occipital bone, which is located at the back of the skull and plays a crucial role in forming the base of the cranium. This bone features a prominent structure known as the occipital protuberance, which is a protruding area that can often be felt as a bony prominence just above the neck. This structure serves as an attachment point for muscles and ligaments that stabilize the head and facilitate movement.

Understanding the skeletal structure is important for hairstylists when considering the overall shape of the client's head and how it may affect the haircut or style. The other options refer to different bones of the skull: the frontal bone is located at the front of the head, the parietal bones are situated on the sides and roof of the skull, and the temporal bones are found at the sides near the ears. Each of these bones has distinct characteristics and locations that differentiate them from the occipital bone.