Cardiac muscle fibers differ from skeletal muscle fibers in that they are -

In the thin filament of skeletal muscle fibre,a small globular protein that masks the active sites for myosin on the $F-$actin,is

$ATP$ase of the muscle is located on:

The central part of the thick filament which is not overlapped by thin filaments is called as:

Total number of muscles in the human body is:

Which of the following statements about the molecular arrangement of actin and myosin are correct?
$I.$ Each actin (thin filament) is made up of $2$ $F$ (filamentous) actins.
$II.$ $F$-actin is the polymer of $G$ (globular) actin.
$III.$ $2$ $F$-actins are twisted into a helix.
$IV.$ Two strands of tropomyosin (protein) lie in the grooves of $F$-actin.
The correct option is: