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': 'The impoant symptom of radiation proctitis is: \nSelect and explain. \nA. Bleeding PR, B. Weight loss, C. Loss of weight, D. Colicky abdominal pain', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Radiation proctitis can lead to persistent rectal bleeding and iron deficiency anemia. Other symptoms include diarrhea, mucoid discharge, urgency, tenesmus, rectal pain and fecal incontinence. Ref: World J Gastroenterol 2011 November 7; 17(41): 4554-4562.', 'role': 'assistant'}]