Cardiac muscle fibres are

The distance or length of the myofibril between two adjacent $Z$-bands is called

Aerobic muscles are called $...A...$ and anaerobic muscles are called $...B....$ Here $A$ and $B$ refer to:

During muscle contraction in a skeletal muscle fibre,$Ca^{2+}$ combines with

Select the correct statement with reference to muscle structure.
$I.$ Each myosin is a polymerized protein.
$II.$ Many meromyosin constitute one thick filament (myosin).
$III.$ Each meromyosin's tail is called heavy meromyosin $(HMM)$ and head is called light meromyosin $(LMM)$.
$IV.$ The globular head is an active $ATPase$ enzyme and has binding sites for $ATP$ and active sites for actin.
Choose the option with correct statements.

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