“Who did it belong to?” asks about alliance membership.
The wording does not mean that one state was another’s property. It asks which political and military bloc the GDR was aligned with. The Warsaw Pact is the specific correct answer.
The comparison helps when reading historical texts: NATO and the Warsaw Pact were different alliances. A report about the Federal Republic at the time therefore cannot simply be applied to the GDR.
The other three answers
Three answers confuse the bloc or deny the alliance connection.
to the Western powers
The GDR was under Soviet influence, not aligned with the Western powers. Western alliance membership belongs to the Federal Republic in this comparison.
to NATO
NATO was the alliance of the Federal Republic at the time. The GDR was not a NATO member.
to the non-aligned states
“Non-aligned” does not fit a state that was a member of the Soviet-led Warsaw Pact.
Alliance, party and army are different things.
The Warsaw Pact was an alliance of several states. The SED was the GDR’s ruling party. These terms describe different levels and are not interchangeable names.
The question concerns a historical classification. It neither says that everyone in the GDR supported its alliance policy nor that the GDR was already a member throughout its existence: the alliance was founded only in 1955.
Warsaw Pact · House of History ↗GDR → Warsaw Pact; Federal Republic at the time → NATO.
Learn both matches as a pair and keep the historical period in mind.
Three words for this question
- das Militärbündnismilitary alliance
- An association of states for military cooperation.
- der Kalte KriegCold War
- The historical East–West conflict referred to in the question.
- blockfreinon-aligned
- Here: not aligned with either of the two major power blocs.