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
Functional unit of muscle: 
Select and explain. 
A. Sarcomere, B. Actin, C. Myosin, D. Troponin
A: Sarcomere
Answer: A: Sarcomere 
Explanation: Functional unit of muscle is : sarcomere It is the pa of myofibril present between two succsive z lines. Ref: Guyton and Hall textbook of medical physiology 12th edition, page number:86,87