The Conversion of Russia to Orthodox Christianity Was Facilitated by What

The conversion of Russia to Orthodox Christianity was facilitated by what factor?

A) Both civilizations were founded by Slavic peoples and shared similar cultural values.
B) The Vikings had forged trade routes from northern Europe to the Black Sea and the Byzantine Empire.
C) Orthodox Christian monks built monasteries along the major water routes into southern Russia.
D) The rulers of Kievan Rus forced Orthodox Christianity on the region in order to benefit from the Christian emphasis on obedience to rulers.