This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
[{'content': 'Carcinoid tumor is diagnosed by. \nSelect and explain. \nA. Urinary 5 HIAA, B. Chromogranin A, C. Neuron specific enolase, D. Urinary 5 Hydroxy tryphtophan', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Urinary 5HIAARef: Bailey 27th edition, Page 1251* Most common used investigation to diagnose carcinoid tumor is 24 hours urinary 5HIAA* IOC to localize the tumor is DOTATATE scan', 'role': 'assistant'}]