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: Physiology
[{'content': 'Function of a muscle spindle is: September 2009 \nSelect and explain. \nA. Regulates withdrawl reflex, B. Maintains muscle tone, C. Feedback device to maintain muscle length, D. Receptor for inverse stretch reflex', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Feedback device to maintain muscle', 'role': 'assistant'}]