Step 3: Examine each option provided:
- Acromion: This is a bony projection on the scapula (shoulder blade), not part of the head.
- Olecranon fossa: This is a depression on the humerus (arm bone), not part of the head.
- Mastoid process: This is a prominent bone marking located on the temporal bone of the skull, near the ear, and is part of the head.
- Medial malleolus: This is a bony prominence on the tibia (leg bone), not part of the head.