How Did Stalin Come to Power

How did Stalin come to power?

A) Lenin named Stalin as his successor before his death in return for Stalin's help suppressing the Bolsheviks.
B) Stalin was narrowly elected due to his honesty and character, running a campaign free of propaganda.
C) The Treaty of Versailles stipulated that Italy must elect a new leader through highly structured, democratic processes.
D) Stalin placed allies in crucial positions in the Communist Party, eventually forcing Trotsky out.
E) Stalin created the Left Opposition against Trotsky and gave non-Communist organizations more power.