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
Best investigative modality for gall bladder - 
Select and explain. 
A. OCG, B. PTC, C. Ultrasound, D. Intravenous cholangiogram
C: Ultrasound
Answer: C: Ultrasound 
Explanation: None