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
Early stage of carcinoma esophagus is diagnosed by ? 
Select and explain. 
A. Barium meal, B. Trans oesophageal USG, C. MRI, D. Endoscopy
D: Endoscopy
Answer: D: Endoscopy 
Explanation: Ans. is 'd' i.e. Endoscopy