For how many years is the state parliament of Saarland elected?

EDITORIAL LEARNING AID

Why is this answer correct?

The state parliament of Saarland is elected for five years; the electoral term begins with the constituting session of the new parliament. Three, four or six years do not correspond to the rule in Saarland and are therefore wrong.

Saarland: state parliament elected for five years.

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