This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Endoscopic ultrasound is extremely useful in staging which tumor? \nSelect and explain. \nA. Cancer colon, B. Cancer esophagus, C. Cancer stomach, D. Cancer head of pancreas', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Cancer esophagusRef: Bailey and Love 26th Edition, Page 990EUS helps in diagnosis and staging of:* Esophageal cancer (Most useful)* Rectal cancer* Gastric cancer* Pancreatic head cancer.', 'role': 'assistant'}]