Which Is TRUE About the Comparison of Excitation-Contraction Coupling in Cardiac

Which is TRUE about the comparison of excitation-contraction coupling in cardiac muscle with that in skeletal muscle?

A) Extracellular Ca²⁺ plays a major role in cardiac but not skeletal muscle.
B) The mechanism  for Ca²⁺ release from the sarcoplasmic reticulum is the same in both types of muscle.
C) Troponin sites are completely saturated immediately after Ca²⁺ release in both types of muscle.
D) There is no net change in total intracellular Ca²⁺ concentration in either muscle.
E) Intracellular Ca²⁺ stores are necessary for contraction in skeletal muscle,but not in cardiac muscle.