Answer :
When Ivan IV (a.k.a. Ivan the Terrible) took power, he named his vast territory Russia.
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The correct answer is Russia.
Ivan IV of Russia was a prince of Moscow and of all Russia. He was the first Russian monarch to adopt the title of tsar since 1547.
He is considered one of the creators of the Russian State. His greatest contributions to his country were the conquest of Siberia, the creation of a new legal code, the Sudébnik, the centralization of power in the capital, the creation of the Zemski Sobor and the Opríchnina .