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: Radiology
[{'content': 'True about features of cholecystitis on USG : \nSelect and explain. \nA. Thick fibrosed gallbladder wall, B. Stone impacted at neck of gall bladder, C. Perigallbladder halo, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A i.e. Thick fibrosed gall bladdar wall; B i.e. Stone impacted at neck of gall bladder; C i.e. Perigall bladdar halo', 'role': 'assistant'}]