During muscle contraction,which of the following events occurs?

Sarcoplasm is the

Which muscle band remains unchanged during the contraction and relaxation of the skeletal muscle?

Which of the following is the contractile protein of a muscle?

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.

Which of the following statements are correct regarding skeletal muscle?
$A$. Muscle bundles are held together by a collagenous connective tissue layer called fascicle.
$B$. Sarcoplasmic reticulum of muscle fibre is a storehouse of calcium ions.
$C$. Striated appearance of skeletal muscle fibre is due to the distribution pattern of actin and myosin proteins.
$D$. $M$ line is considered as the functional unit of contraction called sarcomere.
Choose the most appropriate answer from the options given below: