The functional unit of the contractile system for a striated muscle is:

Body contraction is due to the pulling of ....

The biceps and triceps muscles are found in

Relaxation of the muscle takes place due to
$I.$ Pumping of $Ca^{2+}$ ions into the sarcoplasmic reticulum
$II.$ Presence of $ATP$
$III.$ Conformational changes in troponin and masking of the actin filament
Which of the following options contains the correct statements?

Give the name of the subunits of Troponin.

What is the source of energy for muscle contraction?