Which person was most important for the formation of the soviet union?

Vladimir Lenin was the most important person for the "formation of the Soviet Union".

Explanation:

Vladimir Lenin was the supreme leader of the Bolsheviks that brought down the "provisional Russian government" in October 1917. A treaty was signed in 1922 which led to the formation of the Soviet Union. The proposition of this treaty was a brainchild of Vladimir Lenin. Vladimir Lenin persuaded convince the Ukrainian, the Transcaucasian, the Russian and the Byelorussian republics to sign the treaty of the formation of the Soviet Union.

The answer is c) people evacuated but almost all returned