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: Dental
According to Horning and Cohen staging of oral
necrotizing diseases stage one represents 
Select and explain. 
A. NUG, B. NUP, C. Necrotizing stomatitis, D. Noma
A: NUG
Answer: A: NUG 
Explanation: None