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
Best diagnosis of tracheo-oesophageal fistula is by: 
Select and explain. 
A. Barium sulphate, B. Conray 240, C. Dianosil, D. Urograffin
C: Dianosil
Answer: C: Dianosil 
Explanation: Ans. Dianosil