From what age may one vote in Hesse in local elections?

EDITORIAL LEARNING AID

Why is this answer correct?

In Hesse the voting age for local elections is 18; the general voting age also applies at municipal level there. 14 and 16 are too young, 20 too high.

Hesse: local elections from 18 – unlike Bremen or Hamburg, where it is 16.

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