After Lenin Died,Stalin Became the Soviet Leader

Multiple Choice

After Lenin died,Stalin became the Soviet leader

A) by controlling the party organization and ruthlessly destroying all his rivals.
B) because Lenin had enthusiastically supported him.
C) by denouncing Lenin and promising to undo all his work.
D) in a democratic Politburo election.
E) because he was the only native Russian among the Bolshevik leadership.