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
The upper denture falls when the patient opens his
mouth wide. This is due to: 
Select and explain. 
A. Thick labial flange, B. Over-extended borders, C. Thick disto-buccal flange, D. Poor peripheral seal
C: Thick disto-buccal flange
Answer: C: Thick disto-buccal flange 
Explanation: None