Step 1: Recall classic ATLS. The traditional ATLS primary survey follows A-B-C-D-E (Airway, Breathing, Circulation, Disability, Exposure).
Step 2: Apply the trauma/military modification. When there is catastrophic (exsanguinating) external hemorrhage, the patient can bleed to death before the airway is even secured. Therefore a preceding "C" for Catastrophic hemorrhage control is added in front, giving the <C>ABCDE sequence: control major bleeding first (direct pressure, tourniquet, haemostatic dressing), then proceed Airway to Breathing to Circulation to Disability to Exposure.
Step 3: Choose the option. The correct order is therefore Catastrophic hemorrhage control to Airway to Breathing to Circulation to Disability to Exposure (C-ABCDE). The recall key labels this as the "C-A-B-C-D-E" sequence.
Step 4: Eliminate the others. Plain ABCDE omits the life-saving first step of arresting massive bleeding. Reordering to Circulation-first without specific haemorrhage control, or Disability-first, does not reflect the catastrophic-haemorrhage protocol.
Key fact: With life-threatening external bleeding, follow <C>ABCDE - Catastrophic hemorrhage control comes before Airway.