"You have just taken over an existing work group that has been together for about a year. Your observations suggest that the group is working well. Each group member knows what is expected of him or her, and they are working together productively. Which stage of group development does this group seem to have reached?"
The performing group stage is the stage in which a group reaches its highest performance, hence the name.
In this stage, the members of the group know what is expected of them, and they play their part harmoniously, coordinating their actions toward the common goal.
The group described in the question is clearly in the performing stage because its members are described to be workign together productively.
