The H-zone in the skeletal muscle fibre is due to:

1. The central gap between myosin filaments in the A-band.
2. The central gap between actin filaments extending through myosin filaments in the A-band
3. Extension of myosin filaments in the central portion of the A-band.
4. The absence of myofibrils in the central portion of A-band.

Central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone. ‘H’ zone is also called Hensen’s Line.