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
The most useful method to diagnose upper GI haemorrhage is - 
Select and explain. 
A. Barium study, B. Celiac angiography, C. Gastric biopsy, D. Endoscopy
D: Endoscopy
Answer: D: Endoscopy 
Explanation: None