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: Medicine
[{'content': 'Chemo prevention trials shown effective in reducing of –  a) Lymphoma  b) Breast Ca  c) Pancreatic Ca  d) Ca urinary bladder  e) Aero digestive tract \nSelect and explain. \nA. ab, B. be, C. ace, D. acd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]