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
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: None