This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
[{'content': 'In carcinoma head of pancreas nausea and vomiting is due to \nSelect and explain. \nA. External compression of duodenum, B. Poal vein infiltration, C. Proliferation and infiltration into duodenum, D. Chemotherapy related', 'role': 'user'}, {'content': 'Answer: A \nExplanation: PRESENTING SYMPTOM FREQUENCY Jaundice Weight loss Abdominal pain Nausea/vomiting Pruritus Fever Gastrointestinal bleeding Ref: Sabiston 20th edition Pgno: 1544', 'role': 'assistant'}]