For example, cyclin B forms a Cdkc that controls the M stage of the cell cycle. This Cdkc turns on the proteins that are involved in mitosis, turns off the proteins that prevent mitosis, and even activates an enzyme complex that breaks down cyclin B. The loss of cyclin B signals the end of the M portion of the cycle. Notice that the concentrations of cyclin B peak during the mitosis stage. Based on the above graph, which cyclin forms the primary Cdkc that controls the G2 stage?