The region between two successive $Z-$lines in a myofibril is

Which of the following ions is necessary for the contraction of muscles and nerve impulse transmission?

In a skeletal muscle fiber,what is the $H$-zone?

The sliding filament theory to explain muscular contraction was given by

Which type of muscle is multinucleated during its functional state?

Given below are two statements:
$Statement-I$: Plasma creatinine is produced during catabolism of creatinine phosphate in skeletal muscle contraction.
$Statement-II$: Creatinine phosphate provides a ready source of high-energy phosphate.
In the light of the above two statements, choose the most appropriate answer from the options given below.