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
During skeletal muscle contraction 
Select and explain. 
A. A band shoen, B. Both H & I band shoen, C. Both A & I band shoen, D. Both A & H band shoen
B: Both H & I band shoen
Answer: B: Both H & I band shoen 
Explanation: During muscle contraction, two Z lines come closer, A band remains constant, length of H & I band decreases.Ref: Guyton; 13th edition