The best answer to illustrate that religion was an important element in the English Civil War, the formation of a commonwealth, and the Restoration is:
B) Cavaliers and Roundheads supported opposite sides.
The Cavaliers were generally loyal to the monarchy and were associated with the Anglican Church, while the Roundheads supported Parliament and were often Puritans or dissenters from the Church of England. This division was heavily influenced by religious beliefs and tensions during that period, making it a significant aspect of the conflict.