Ivan the Great Gave Further Substance to the Idea That

Ivan the Great gave further substance to the idea that Muscovy was the heir to Rome after the fall of Constantinople by:

A) making Greek the official language of Muscovy.
B) adopting the use of the Roman phalanx in his army.
C) encouraging his subjects to adopt Roman Catholicism.
D) attacking Constantinople in an attempt to dislodge it from Ottoman control.
E) marrying the niece of the last Byzantine emperor.