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
Investigation of choice for submandibular sialolithiasis is 
Select and explain. 
A. Sialography, B. CT scan, C. USG, D. X-ray
D: X-ray
Answer: D: X-ray 
Explanation: X ray is IOC for submandibular sialolithiasis as most of the stones are radio-opaque.