You are answering a USMLE-style medical question. Question: A 6-year-old Russian boy who recently immigrated to the United States presents to your office with fever and dyspnea. On examination of the oropharynx, you note a grayish-white pseudomembrane and uneven elevation of the soft palate. The patient displays marked enlargement of the cervical lymph nodes. Which of the following describes the organism responsible for this patient's disease? Options: A) Yeast with pseudohyphae B) Gram-positive bacteria producing exotoxin that acts via ADP ribosylation C) Gram-positive cocci with hyaluronic acid capsule D) Gram-negative encapsulated bacteria producing IgA protease Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.