Identify the bone that forms the base of the skull.

The occipital bone is the correct choice as it is specifically known for forming the base of the skull. This bone is located at the posterior part of the skull and is critical in providing structural integrity and support for the brain. It also contains the foramen magnum, which is the large opening through which the spinal cord passes, connecting the brain to the central nervous system.

The occipital bone plays a vital role in articulating with the vertebrae at the back of the skull, highlighting its importance in both the skeletal structure and functionality. Its shape and position are uniquely designed to support the weight of the head and protect the brain.

In contrast, the frontal bone forms the forehead and is primarily located at the front of the skull, the temporal bones are located on the sides and house structures of the ear, and the parietal bones sit atop the skull and are involved in forming the sides and roof of the cranium. These bones serve different purposes and are not positioned to form the base of the skull.