How Did the Soviet Union's Treatment of Czechoslovakia in 1948

How did the Soviet Union's treatment of Czechoslovakia in 1948 demonstrate its intention to consolidate its hold on eastern Europe?

A) When Czechoslovakia sought to declare itself a neutral power in the conflict between the Soviet Union and the United States, Stalin ordered Soviet troops to invade and seize the government.
B) Despite local protests, the Soviet Union established a massive military base in Czechoslovakia in order to easily send troops throughout central Europe.
C) Even though the Czech Communist Party had won significant electoral support, Stalin still orchestrated the overthrow of the government and establishment of a one-party Communist dictatorship.
D) When Czechoslovakia appealed to the United States for aid, the Soviet Union forbade the aid and any Western officials from entering Czech territory.