An 18-year-old girl complains of general weakness, a fever of 38.2°C, and moderately sore throat. Examination shows hyperemic mucosa of the posterior pharyngeal wall with a cyanotic tint. The tonsils are enlarged and partially covered in islets of white gray dense filmy deposits. The deposits are difficult to remove and expose a bleeding surface when removed. Palpation detects moderately painful regional lymph nodes 15 cm in size. Make the provisional diagnosis.