Unstriped smooth muscles are found in

Based on their location in the human body or animals,the types of muscles are:
$I.$ Skeletal
$II.$ Visceral
$III.$ Cardiac
$IV.$ Non-visceral
The correct option is:

How many main types of muscles are there?

In a $A$ state,the edge of thin filaments on either side of thick filaments $B$ overlap the free ends of $C$ filaments leaving the central part of thick filaments. This central part of thick filament,not overlapped by thin filaments is called $D$ zone.
Choose the correct options to fill the gaps $A, B, C$ and $D$,so as to complete the given $NCERT$ statement.

What happens when a sub-threshold stimulus is applied to a muscle?

Striated muscles contract by