Which part of a muscle cell is the storehouse of calcium ions?

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:

Red muscle fibres are rich in

Myofilaments or myofibrils are

The muscles involved in the movement of the arm are

Where is troponin found during muscle contraction?