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
Mandibular ridge resorption causes 
Select and explain. 
A. Widening of posterior ridge, B. Widening of anterior ridge, C. Narrowing of posterior ridge, D. Widening of maxillary residual ridge
A: Widening of posterior ridge
Answer: A: Widening of posterior ridge 
Explanation: None