Which of the following is the result of an inward Na+ current?

A、UpstrokeoftheactionpotentialintheSAnode
B、UpstrokeoftheactionpotentialinPurkinjefibers
C、Plateauoftheactionpotentialinventricularmuscle
D、Repolarizationoftheactionpotentialinventricularmuscle
E、RepolarizationoftheactionpotentialintheSAnode.