This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tonsils, Subject name: ENT
All of the following cause a grey white membrane on the tonsil, 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: (b) Ludwig's angina(Ref. Scott Brown, 8th ed., Vol 3; 550)Ludwig's angina is cellulitis of the sub-mandibular space.The rest of the options can cause membrane over tonsils.