107. A 3-year-old girl presents to the emergency department with fever, hoarseness, a “seal bark-like” cough, and inspiratory stridor. Her father states that she has had a cold for the past few days, with runny nose, nasal congestion, sore throat, and cough. He is now concerned because her cough has now become loud, harsh, and brassy. Which of the following is the most likely cause of her ailment? *