This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rectum and anal canal, Subject name: Surgery
[{'content': 'The length of the flexible sigmoidoscope is: \nSelect and explain. \nA. 60 cm, B. 70 cm, C. 80 cm, D. 90 cm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Instruments Length Proctoscope 10 cm Rigid sigmoidoscope 25 cm Flexible sigmoidoscope 60 cm Colonoscope 160 cm', 'role': 'assistant'}]