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
48 year old male reported with the chief complaint of ulcer on the gums and on general examination headache, fever and malaise was observed. On oral examination, sharply punched out crater-like erosions of the interdental papillae of sudden onset were noted. The patient also complained of bad breath.

This patient's lower anterior marginal gingiva showed comma-shaped defect called 
Select and explain. 
A. Stillman's cleft, B. Dehiscence, C. Fenestration, D. Cul-de-sac
A: Stillman's cleft
Answer: A: Stillman's cleft 
Explanation: None