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
Clinical feature of mouth breathing is: 
Select and explain. 
A. Pigeon face appearance, B. Proclined mandibular anteriors, C. Shallow and flat maxillary arch, D. Retroclined maxillary anteriors
A: Pigeon face appearance
Answer: A: Pigeon face appearance 
Explanation: None