Which German state had a black-red-gold flag with a hammer, compass and wreath of grain?

EDITORIAL LEARNING AID

Why is this answer correct?

Hammer, compass and wreath of grain were the symbols in the state emblem of the GDR and from 1959 also appeared on its flag. Prussia used black and white, and the "Third Reich" black-white-red with a swastika. The flag of the Federal Republic is black-red-gold without symbols.

GDR flag: hammer, compass, wreath of grain.

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