Caesar Augustus was originally named Octavian, great nephew of Julius Caesar. He was the first emperor of the Rome and was named Augustus. Augustus during this time was known for placing Rome in the "Pax Romana" a state of amazing excellency during ancient Roman times. Since Augustus placed Rome into a period of greatness, it does not make sense that he sent Rome into a civil war, meaning it can't be a. For choice b., it is describing Nero, who supposed played his lyre while the city of Rome burned. Choice d is referring to Julius Caesar; well in partial. Julius Caesar created a calendar but I do not remember if he really referred to himself as a god. So this only leaves option c. He established an imperial government in place of the Roman Republic.
