Which present-day German federal state formerly belonged to the territory of the GDR?

EDITORIAL LEARNING AID

Why is this answer correct?

Saxony-Anhalt belonged to the Soviet occupation zone and was part of the GDR until 1990; the state was re-established in 1990. Hesse and North Rhine-Westphalia lay in the western zones, the Saarland in the French zone. Those three belonged to the Federal Republic.

Saxony-Anhalt was GDR territory.

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