This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
Investigation for assessing proper functioning of biliary system 
Select and explain. 
A. USG, B. CT scan, C. HIDA scan, D. All of the above
C: HIDA scan
Answer: C: HIDA scan 
Explanation: HIDA Allows visualization of the biliary tree and gallbladder Presence of inflammation around GB Occasionally, presence of stones within thr biliary tree GB is visualizer within 30 minutes of isotope injection in 90% of normal individuals and within 1 hour in the remainder The bowel is usually seen within 1 hour in the majority of patients Nonvisualization of the GB is suggestive of acute cholecystitis If the patient has contracted gallbladder, as often occurs in chronic cholecystitis, GB visualization may be reduced or delayed Ref:Sabiston 20th edition Pgno :1488