'Oxygen debt' is the amount of oxygen required for

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:

$A-$ Actin filaments occur in two forms: the monomeric $G$-actin and the polymeric $F$-actin.
$R-$ Tropomyosin is a rod-shaped fibrous protein. Tropomyosin forms two helical strands,which are wrapped around the $F$-actin filaments.

Cardiac muscle fibres are

What is the state of sustained muscle contraction without relaxation between successive stimuli called?

Which of the following interacts with skeletal muscles to produce movement?