Prior to drawing blood for blood gas analysis, the nurse conducts the modified Allen test to ensure there is adequate collateral circulation. The nurse asks the client to extend the wrist over a rolled towel and make a fist. Place the following steps (Roman numerals) in order from first to last.

B Palpate the ulnar and radial pulses and apply pressure to both arteries. C Observe the hand for color. A Ask the client to open and close the hand until the skin blanches. D Release the ulnar artery while maintaining pressure on the radial artery.