The storehouse of calcium ions in the muscle fibre is

Which of the following muscles act involuntarily?
$(a)$ Striated muscles $(b)$ Smooth muscles
$(c)$ Cardiac muscles $(d)$ Skeletal muscles

It is known that red muscle fibres in animals can work for longer periods of time continuously. How is this possible?

The largest muscle in the human body is:

The largest smooth muscle is present in:

Contractile tissues have the following features:
$(i)$ Mesodermal in origin
$(ii)$ They contain stretch receptors
$(iii)$ Rhythmic contractions are seen in them
$(iv)$ They do not fatigue during the life of the animal
Which of the above are characteristics of sphincters?