From what age may one vote in local elections in Lower Saxony?

EDITORIAL LEARNING AID

Why is this answer correct?

In Lower Saxony, young people from the age of 16 may already vote in local elections and thus help decide the local council and the mayor. 14 is too young, 18 applies to state and federal elections, and 20 is too high.

Local elections from 16, state and federal elections from 18.

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