The answer is B high pressure.
A concussion, which is a form of mild traumatic brain injury, occurs after a blow to the head. The brain is surrounded by fluid and protective membranes called meninges, which usually cushion the brain. During an impact, the brain is pushed against the inside of the skull and can be bruised.
Explanation:
It is given that,
Length of the helicopter, l = 3.1 m
The helicopter rotates, the length of helicopter will become the radius of circular path, r = 3.1 m
Angular speed of the helicopter, 
(a) The centripetal acceleration in terms of angular velocity is given by :



(b) Let v is the linear speed of the tip. The relation between the linear and angular speed is given by :


v = 90.89 m/s

Hence, this is the required solution.