The refractory period of a muscle fibre in mammals is:

$I.$ Sarcoplasmic reticulum are abundant
$II.$ Myoglobin content is high
$III.$ Sarcoplasmic reticulum are moderate
$IV.$ Aerobic muscles
$V.$ Depends on anaerobic respiration for energy
$VI.$ Less myoglobin content
Select the option with correct statements for red muscle.

Which protein is present in muscles?

What is the source of energy for muscle contraction?

Sarcoplasmic reticulum is present in which structure:

Actin filament is made up of