A 23yrs male falls on the ground when he is struck in the right temple by a baseball.While being driven to the hospital,he lapses into coma.He is unresponsive with the dilated right pupil when he reaches the emergency department.Which of the following is the most important step in initial managament ?

• A. X-ray of the skull and cervical spine
• B. Doppler ultrasound examination of the neck
• C. Craniotomy
• D. CT scan of the head