This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach & Duodenum, Subject name: Surgery
[{'content': 'Simplest investigation to be performed for suspected cancer stomach: \nSelect and explain. \nA. Double contrast radiography, B. Plain X ray, C. CT scan, D. Endoscopy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Double contrast radiographyRef: Harrison 18th Edition, Page 766* Simplest first investigation: Double contrast radiography* If ulcer is found: Endoscopy must be done to take biopsy', 'role': 'assistant'}]