The correct answer is converted to christian orthodox.
In 988 Vladimir prince of Kiev converted to christian orthodox in order to help to unify people.
The father of Vladimir was a prince in Rurik dynasty. Vladimir took over after the death of his father in 972. Before Vladimir taking over his father's post, he was a prince in Novgorod.
Vladimir consolidated the realm of Kievan from Ukraine, Baltic sea, Belarus and Russia. He unified people against Baltic tribes. eastern nomads and incursion of Bulgarian.
Those who were the followers of slavic paganism were being converted to christians by Vladimir and they were then christianized by Kiev Rus'
