At which site do muscle fibers receive stimulation from a motor neuron?

Sliding filament theory can be best explained as

Which bands contain only actin and only myosin filaments,respectively?

Which of the following statements are false regarding the muscle structure?
$I.$ In the centre of each $I$-band is an elastic fibre ($Z$-line) which bisects it.
$II.$ Thin filaments are firmly attached to the $Z$-line.
$III.$ $M$-line is a fibrous membrane in the middle of $A$-band.
$IV.$ $A$ sarcomere comprises one full $A$-band and two half $I$-bands.

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

If a muscle fails to give stimulation action and there is much ingestion of lactic acid,the condition is termed as