Choose the correct option for the following:
Biceps $\quad$ Iris $\quad$ Heart

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:

Which of the following ions is essential for muscular contraction?

Name the connective tissue sheath which surrounds the muscle bundles.

Myofilaments or myofibrils are

The strongest muscles in the human body are found in the: