The "myosin binding site" is present on:

The dark bands ($A$-bands) of a skeletal muscle are known as

$A-$ Visceral muscles do not show any striations and are smooth in appearance. Hence,they are known as non-striated muscles.
$R-$ Their activities are under the voluntary control of the nervous system.

The immediate source of energy for muscle contraction is ...... .

$A$ human body contains how many muscles?

$A$: All muscles follow the 'All or None' principle.
$R$: All muscles contract either fully or not at all depending upon the availability of a threshold stimulus.