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
The site where myosin heads bind to actin in skeletal muscles are covered by: 
Select and explain. 
A. Tropomyosin, B. Troponin, C. Calcium, D. None of the above
A: Tropomyosin
Answer: A: Tropomyosin 
Explanation: A i.e. Tropomyosin