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 grey-white membrane in the throat except - 
Select and explain. 
A. Streptococcal tonsillitis, B. Diphtheria, C. Ludwig's angina, D. Adenovirus pharyngitis
C: Ludwig's angina
Answer: C: Ludwig's angina 
Explanation: Causes of the membrane in the throat (Differential diagnosis of the membrane over the tonsil) 

Pyogenic membranous tonsillitis
Infectious mononucleosis
Traumatic ulcers
Vincent's angina
Agranulocytosis
Adenovirus pharyngitis
Candidal infection of tonsil
Leukemia
Diphtheria
Aphthous ulcers