Q. A 5-year-old boy is brought to the pediatric clinic by his mother, who reports that her son has had a fever, sore throat, and difficulty swallowing for the past 2 days. His vital signs are as follows: temperature 39.0°C (102.2°F), heart rate 95 beats/min, respiratory rate 20 breaths/min, and blood pressure 100/65 mm Hg. On examination, the child appears uncomfortable and has small whitish patches on his upper palate and throat. What is the most likely causative agent for this patient's condition?