This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'True about troponin: \nSelect and explain. \nA. Has 3 sub units, B. Troponin c binds to calcium, C. Troponin I binds actin and tropomyosine, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Troponin is a complex protein: It has C,I,T sub units C binds to calcium Ref: Guyton and Hall textbook of medical physiology 12th edition, page number 89', 'role': 'assistant'}]