Answer: D. Vladimir
Vladimir the Great was a grand prince of Kiev, and ruler of Kievan Rus from 980 to 1015.
Vladimir converted to Christianity in 988. Afterwards, he exhorted the residents of Kiev to the river for baptism. He asked all residents, "rich and poor, beggars and slaves" to come to the river, unless they wanted to become the prince's enemies. They were converted to Christianity, and this mass conversion started the Christianization of Kievan Rus.
