This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharynx, Subject name: ENT
Pseudomembrane over tonsil and pharynx is caused by 
Select and explain. 
A. Gram positive bacili, B. Gram negative bacili, C. SS RNA virus, D. Catalase negative cocci
A: Gram positive bacili
Answer: A: Gram positive bacili 
Explanation: Pseudomembrane is formed in diphtheria, which is caused by Corynebacterium diphtheria, which is a gram-positive bacillus Ref: Harshmohan textbook of pathology; 7th edition