The correct answer is OB. Both played a large role in uniting people across large regions.
Christianity and Islam, during the postclassical period, had significant impacts on society in various regions. Both religions spread widely and had the ability to bring together diverse groups of people, transcending geographical boundaries. They served as unifying forces, fostering a sense of community and shared beliefs among their followers. This contributed to the formation of cohesive societies across large regions influenced by these religions.