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
Actin's active site is covered by 
Select and explain. 
A. Myosin, B. Tropomyosin, C. Troponin, D. Desmin
B: Tropomyosin
Answer: B: Tropomyosin 
Explanation: The active site of actin in skeletal muscles is where myosin binds. This is covered by Tropomyosin.