Final answer:
Poland, Hungary, and East Germany joined the Warsaw Pact primarily for mutual defense against NATO and political alignment with the Soviet Union, not just for economic cooperation or access to military technology.
Step-by-step explanation:
Poland, Hungary, and East Germany joined the Warsaw Pact primarily for B) Mutual defense against NATO. This was in response to the formation of NATO, a collective defense alliance that included Western European countries united to protect themselves against potential Soviet aggression. Following the creation of NATO, the Soviet Union saw the need to establish a similar military alliance to safeguard its interests and Communist ideologies in Eastern Europe. This led to the forming of the Warsaw Pact in 1955, which was comprised of the Soviet Union and its Eastern European satellite nations, serving as a counterbalance to NATO and as a formalization of the division of Europe into the Western and Eastern Blocs. Thus, the main purpose of the Warsaw Pact was collective defense and political alignment with the Soviet Union, rather than economic cooperation or solely access to military technology and support.