Which of These Statements Correctly Describes Action Potentials in the Heart

Multiple Choice

Which of these statements correctly describes action potentials in the heart?

A) The rising phase of the action potential in cardiac autorhythmic cells is due to a rapid Ca²⁺ influx.
B) The rising phase of the action potential in cardiac contractile cells is due to a rapid K⁺ influx.
C) The plateau phase of the action potential in cardiac contractile cells is due to a rapid Ca²⁺ influx.
D) The plateau phase of the action potential in cardiac contractile cells is due to a rapid K⁺ influx.