Read the following passages and answer the questionthat follow: A major difference between the two superpowers and their respective empires was that the Roman Empire was culturally much more diverse than that of Iran. The Parthians and later the Sasanians, the dynasties that ruled Iran in this period, ruled over a population that was largely Iranian. The Roman Empire, by contrast, was a mosaic of territories and cultures that were chiefly bound together by a common system of government. Many languages were spoken in the empire, but for the purposes of administration Latin and Greek were the most widely used, indeed the only languages. The upper classes of the east spoke and wrote in Greek, those of the west in Latin, and the boundary between these broad language areas ran somewhere across the middle of the Mediterranean, between the African provinces of Tripolitania (which was Latin speaking) and Cyrenaica (Greek-speaking). All those who lived in the empire were subjects of a single ruler, the emperor, regardless of where they lived and what language they spoke. Which empire was bound together by a common system of government and why?