Final answer:
The most likely area of a helmet to be impacted in an accident is the brain-case portion of the skull. Protecting this area with a helmet is important to prevent serious head injuries.
Step-by-step explanation:
The most likely area of a helmet to be impacted in an accident is the brain-case portion of the skull. Strong blows to this area can produce fractures, such as linear fractures where fracture lines radiate from the point of impact. Other fracture types include comminuted fractures where the bone is broken into several pieces, or depressed fractures where the fractured bone is pushed inward. It is important to protect this area with a helmet to prevent serious head injuries.