This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Surgery
A 40-year-old female have a right hypochondriac pain. USG is taken. What is the inference? 
Select and explain. 
A. Gall stone, B. Cholecystitis, C. Porcelain gall bladder, D. Cholangiocarcinoma
A: Gall stone
Answer: A: Gall stone 
Explanation: USG shows highly reflective echogenic focus within the gallbladder lumen, with prominent posterior acoustic shadowing, characteristic of Cholelithiasis. If there is associated cholecystitis, gallbladder wall thickening along with the pericholecytic fluid. Murphy&;s sign might be elicited with probe over gallbladder.