How was Joseph Stalin able to become leader of the Communist Party in Russia after Lenin's death?

A)Lenin believed that Stalin would be a fair and honest leader, so he ensured Stalin's position before he died.

B)Lenin had groomed Stalin to be the next Communist leader, and other politicians were afraid to resist Lenin's wishes.

C)Stalin suppressed Lenin's wishes that Stalin NOT follow him as leader of the Soviet Union, fearing Stalin's approach to power.

D)Stalin had been like a son to the childless Lenin and therefore he inherited the position from Lenin after his death.