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.