The best answer to this (of the ones you suggest) is B. The Soviets created the Warsaw Pact to make their control over Eastern Europe more secure.
The Warsaw Pact was created to be a counterbalance to the United States and its NATO alliance. The Soviets created the pact in part to try to ensure that the Western nations would not be able to overrun them.
However, a major purpose of the Warsaw Pact was to pull the countries of Eastern Europe closer to the Soviet Union. As the salem-history link below says,
The period following Stalin’s death in 1953 had seen considerable diversity and agitation for increased independence on the part of the Eastern European satellite states...
It was in response to these actions that the Soviets created the Warsaw Pact.