Which of the following does not consist solely of involuntary muscles?

During muscle contraction in humans,the:

The special contractile protein actin is found in

Which ion is essential for muscle contraction?

In striated muscle contraction:

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.