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': 'The site where myosin heads to action in skeletal muscles are covered by \nSelect and explain. \nA. Tropomyosin, B. Troponin o, C. Calcium, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In resting muscle, troponin I is bound to actin and tropomyosin covers the site where myosin head interacts with actin. Ref: Ganong&;s Review of medical physiology;25th edition; pg: 104.', 'role': 'assistant'}]