This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Most distinguishable feature between skeletal and smooth muscle is the presence of ------ in smooth muscle 
Select and explain. 
A. Troponin, B. Tropomyosin, C. Myosin, D. Actin
A: Troponin
Answer: A: Troponin 
Explanation: Actin, myosin & tropomyosin are present in both skeletal muscle & smooth muscle, but troponin is absent in smooth muscle