The correct answer is C. Sunni Islam spread throughout the Eastern Mediterranean region.
What describes a long-term effect of the Ottoman Empire's reign is Sunni Islam spread throughout the Eastern Mediterranean region.
Considered one of the largest empires in the history of humanity, the Ottoman Empire was base on Islam. The Ottoman Empire was the most powerful empire in the Eastern Mediterranean. The best moments of dominance were in times of Suleiman the Magnificent, who ruled from 1520 to 1566. In those years the empire covered what today are the territories of Turkey, Lebanon, Egypt, Greece, Syria, Bulgaria, Romania, Macedonia, Hungary, Palestine, and Jordan.