Stalin Was Convinced That Soviet Security Rested Upon Creating a Buffer

Stalin was convinced that Soviet security rested upon creating a buffer of friendly neighboring states,mainly because

A) those neighbors disapproved of communism.
B) he needed a buffer between his country and China.
C) he wanted to make it impossible for Germany to ever invade Russia again, as it had previously.
D) he wanted access to natural resources that these countries possessed and his own country lacked.
E) the other Allies were talking about the possibility of forming NATO, and his country would not meet the criteria.