What Is One Reason Muscovy Emerged as the Dominant Russian

What is one reason Muscovy emerged as the dominant Russian state with the decline of Mongol control?

A) The Russian Orthodox Church viewed Moscow as the Third Rome or seat of the Holy Roman Empire.
B) Czar Ivan III never married, which allowed him to foster key alliances with queens across Europe.
C) The capital of the Rus state, Kiev, was strategically situated in the heart of Muscovy.