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
Elasticity of hea muscle mainly depends on 
Select and explain. 
A. Myosin, B. Acitn, C. Titin, D. Troponin
C: Titin
Answer: C: Titin 
Explanation: 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