You have arrived on the scene at a high school football field where a​ 17-year-old male is lying on the ground. He is unresponsive and​ cyanotic, and he is making obvious respiratory effort without moving adequate amounts of air. Which of the following should be done​ first?A. Apply​ high-concentration oxygen by nonrebreather mask.B. Insert a nasopharyngeal or oropharyngeal airway.C. Assist ventilations with a​ bag-valve-mask device and supplemental oxygen.D. Open the​ patient's airway using a manual maneuver.