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: Surgery
Submandibular calculus can be removed by: 
Select and explain. 
A. Dilatation of the duct, B. Excision of the opening of duct, C. Removal of the gland, D. Incision of the duct and removal of calculus
D: Incision of the duct and removal of calculus
Answer: D: Incision of the duct and removal of calculus 
Explanation: None