Striped and branched muscles are found in

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

Where are $ATPase$ enzymes located in a muscle fiber?

Which characteristic is $NOT$ associated with white muscle fibers?

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.

Sarcolemma is the covering of