The functional unit of the contractile system in the striped muscle is

Select the correct option for the following statements:
$(i)$ The most important respiratory organ in frogs is the skin / lungs.
(ii) Skeletal muscle / Cardiac muscle exhibits rhythmic contraction.

The covering around a bone is called:

Rahul exercises regularly by visiting a gymnasium. Of late,he is gaining weight. What could be the reason? Choose the correct answer and elaborate.
$A$. Rahul has gained weight due to accumulation of fats in the body.
$B$. Rahul has gained weight due to increased muscle mass and loss of fat.
$C$. Rahul has gained weight because his muscle shape has improved.
$D$. Rahul has gained weight because he is accumulating water in the body.

The biceps and triceps muscles are found in

Which of the following muscles are not under the voluntary control of the nervous system?