The primary survey follows ABC before D (Disability/GCS). In brain injury, hypotension causes secondary brain injury and raises mortality, so correcting hypotension is the most important initial management step. D (determine the GCS) is an assessment done in the 'Disability' step and defines how severe the injury is. The old bank chose D, and the stem never mentions hypotension, so the item is ambiguous. CT brain and an NG tube come later.