Which German city was divided into four sectors after the Second World War?

EDITORIAL LEARNING AID

Why is this answer correct?

Berlin was divided into four sectors and administered jointly by the four Allies. Munich lay in the American zone and Dresden in the Soviet zone. Frankfurt (Oder) belonged to the Soviet zone and was not divided into sectors.

Berlin: four sectors, four Allies.

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