Which of the following correctly identifies a difference between action potentials in cardiac and skeletal muscle?

• A. Skeletal muscles utilize K$^+$ and Ca$^+$$^2$ during action potentials while cardiac contractile cells use K$^+$ and Na$^+$.
• B. Action potentials in cardiac contractile and cardiac pacemaker cells are longer lasting than action potentials in skeletal muscle.
• C. Cardiac pacemaker cells have a slow repolarization while skeletal muscles have a slow depolarization.
• D. The action potentials in each type of tissue are the same.