In addition to being adjusted to the ideal height, what separation should there be between the headrest and the head for it to be effective?
A)The maximum possible and never less than 5 centimeters.
B)Greater than 10 centimeters.
C)The minimum possible and never greater than 4 centimeters.Correct
# Explanation
The headrest must be adjusted as close as possible to the head to be effective in case of a collision, with a **maximum separation of 4 centimeters**. A greater distance significantly reduces its ability to protect against cervical injuries (whiplash), since the neck extends dangerously before the headrest acts.