Answer: sternum: long bone
Step-by-step explanation:
Among the options given, sternum: long bone is the mismatched pair.
Sternum or breastbone is a flat bone that is located in the central part of the chest region. It connects the bones of the ribs with the cartilage. This makes up the rib cage which is a bony cage that provides protection to the vital organs of the body that are lungs, and heart. Also protects the injury of major and important blood vessels. Hence, protects the organs and blood vessels from injuries.