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
The dye used for OCG is: 
Select and explain. 
A. lopanoic acid, B. Sodium diatrozite, C. Biligraffin, D. Meglumine iodothalamate
A: lopanoic acid
Answer: A: lopanoic acid 
Explanation: Ans. lopanoic acid