Which characteristic is $NOT$ associated with white muscle fibers?

What is the full form of the following terms used in muscle structure?
$(1)$ $A$-disc
$(2)$ $I$-disc

Arrange the following steps of muscle contraction in the sequence of events occurring first:
$I.$ Receptor sites on sarcolemma
$II.$ Nerve impulse
$III.$ Release of $Ca^{2+}$
$IV.$ Acetylcholine release
$V.$ Shortening of sarcomere
$VI.$ Synaptic cleft
$VII.$ Spread of impulse over sarcolemma on $T$-tubule
The correct option is:

According to the sliding filament theory:

Which muscle is responsible for changes in body posture?

$A-$ 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.