This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
All of the following cause a gray-white membrane on the tonsils, except: 
Select and explain. 
A. Infectious mononucleosis, B. Ludwig's angina, C. Streptococcal tonsillitis, D. Diphtheria
B: Ludwig's angina
Answer: B: Ludwig's angina 
Explanation: Ludwigs angina is cellulitis of submandibular space. It does not lead to membrane formation over tonsils.