$I-$bands of myofibrils are bisected by

Cardiac muscle fibers differ from skeletal muscle fibers in that they are -

Which one of the following takes place in a myofibril when skeletal muscle contracts?
$A$-band (Dark band) | $I$-band (Light band) | $H$-zone

$M-$line passes through the centre of

How is $G$-actin converted into $F$-actin?

The strongest muscle in the human body is the ......