To which side did the GDR belong during the Cold War?

EDITORIAL LEARNING AID

Why is this answer correct?

From 1955 the GDR was a member of the Warsaw Pact, the military alliance led by the Soviet Union. NATO was the Western alliance to which the Federal Republic belonged; the Western powers were the USA, Great Britain and France. Non-aligned states such as Austria or Yugoslavia belonged to neither bloc.

East = Warsaw Pact, West = NATO.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.