Bone-dissolving cells are known as..........

The membrane sarcolemma is found over

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:

$A$ ...... muscle rotates the forearm to turn the palm downwards.

The contractile protein of skeletal muscle involving ATPase activity is

The monomeric protein which polymerises to form myosin is