Final answer:
The Anabaptists are the group that advocated for complete separation of church and state, adult baptism, and the concept of a church as a voluntary association of reborn believers.
Step-by-step explanation:
The religious group being referred to is the C) Anabaptists. The Anabaptists emerged during the Protestant Reformation and were distinct in their belief in adult baptism over infant baptism, advocating for a separation of church and state.
They held that the true Church was a volunteer association of believers who experienced a spiritual rebirth and then chose to be baptized.
This was in line with their reading of early Christian practices and teachings. Because of their principles, such as the refusal to hold public office or serve in the army, they were seen as radical and often faced persecution.
The religious group being referred to is the Anabaptists. During the Reformation, the Anabaptists sought to return to early Christian teachings and practices. They believed in the separation of church and state and argued that the true Church should be a voluntary association of believers who had undergone a spiritual rebirth and baptism.