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
Which is Not required for visualisation of gall bladder in oral cholecystography: 
Select and explain. 
A. Functioning liver, B. Motor mechanisms of gall bladder, C. Patency of cystic duct, D. Ability to absorb water
B: Motor mechanisms of gall bladder
Answer: B: Motor mechanisms of gall bladder 
Explanation: B i.e. Motor mechanism of Gall bladdar Oral Cholecystography (Graham - Cole - Test) OCG was introduced in 1924 by Graham & Cole. - Na/Ca-Iopanoic acid (TelepaqueQ / Biloptin/ Solubiloptine) dye is used as contrast media. - 3 gmQ of dye is given & X Rays are taken at an interval of 12-15 hours. - USG has replaced itQ.