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 the most reliable diagnostic method for staging the oesphageal cancer? 
Select and explain. 
A. MRI, B. Endoscopic ultrasound, C. CT scan, D. Thoracoscopy
B: Endoscopic ultrasound
Answer: B: Endoscopic ultrasound 
Explanation: Ans. is 'b' i.e., Endoscopic ultrasound