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': 'Elasticity of hea muscle mainly depends on \nSelect and explain. \nA. Myosin, B. Acitn, C. Titin, D. Troponin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Titin, the largest known protein (with a molecular mass near 3,000,000 Da), connects the Z lines to the M lines and provides scaffolding for the sarcomere. It contains two kinds of folded domains that provide muscle with its elasticity.Ref: Ganong&;s Review of medical physiology 25th edition. Page: 101', 'role': 'assistant'}]