For how many years is the Landtag of Brandenburg elected?

EDITORIAL LEARNING AID

Why is this answer correct?

The Brandenburg Landtag in Potsdam is elected for five years. Three and six years are unusual for state parliaments, and four years apply to the Bundestag, not to the Landtag.

Brandenburg Landtag: every five years in Potsdam.

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