This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Which of the following contains site of attachment of calcium ions that initiates muscle contraction? 
Select and explain. 
A. Troponin I, B. Troponin T, C. Troponin C, D. Myosin
C: Troponin C
Answer: C: Troponin C 
Explanation: Troponin T binds the troponin components to tropomyosin; troponin I inhibits the interaction of myosin with actin; and troponin C contains the binding sites for the Ca2+ that helps to initiate contraction.
Ganong 23 rd ed, pg 96