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
The length of the flexible sigmoidoscope is: 
Select and explain. 
A. 60 cm, B. 70 cm, C. 80 cm, D. 90 cm
A: 60 cm
Answer: A: 60 cm 
Explanation: Instruments Length Proctoscope 10 cm Rigid sigmoidoscope 25 cm Flexible sigmoidoscope 60 cm Colonoscope 160 cm