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 filament is not present in which of the band zones? 
Select and explain. 
A. H band, B. I band, C. M band, D. Z band
A: H band
Answer: A: H band 
Explanation: The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin. H-band is the zone of the thick filaments that is not superimposed by the thin filaments.