This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
[{'content': 'Tapping the patellar tendon with a reflex hammer produces a brief contraction of the knee extensors. What is the cause of the muscle contraction? \nSelect and explain. \nA. Elastic rebound of muscle connective tissue, B. Golgi tendon organ response, C. Muscle spindle activation, D. Muscle spindle unloading', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. Muscle spindle activationMuscle spindles monitor muscle length. If the muscle is suddenly stretched, the spindle produces action potentials that activate homonymous motor neurons to contract the stretched muscle and resist the length change.', 'role': 'assistant'}]