The stage labelled C in the diagram is the G2 PHASE.
The cell cycle is divided into G1, S, G2 and M phases. The G2 phase is part of the phases of eukaryotic cell cycle. It is the second stage of interphase, it always occur after the completion of S phase. G2 is the stage, where the cell undergo more growth, produce more proteins and check the replicated DNA in order to verify that the cell is ready to enter into the mitosis phase.