In a contracted skeletal muscle fibre,

Select the correct option for skeletal muscle.
$(I)$ In human body,it is made of a number of muscle bundles.
$(II)$ Muscle bundles contain a number of muscle fibers and each fiber is lined by the sarcolemma.
$(III)$ In a muscle fiber,the sarcoplasm contains only one nucleus.
$(IV)$ In a muscle fiber,the sarcoplasmic reticulum is the storehouse of calcium ions.

$I-$bands of myofibrils are bisected by

Which one of the following pairs of chemical substances is correctly categorized?

Least blood supply is present in which of the following?

Actin filament is made up of