A 6-year-old boy who had a mild respiratory tract infection for 2 days awakens in the middle of the.

A 6-year-old boy who had a mild respiratory tract infection for 2 days awakens in the middle of the night with shortness of breath and difficulty breathing, and his parents bring him to the emergency room. His respiratory rate is 36 breaths per minute and his heart rate is 150 beats per minute. He has a prolonged expiratory phase when breathing. He is afebrile. Lung auscultation reveals high-pitched, squeaky, musical breath sounds in all lung fields during inspiration and expiration. Which of the following is the most likely diagnosis? a. Epiglottitis b. Asthma c. Croup d. Tonsillitis e. Pneumonia