What is the head of government in Brandenburg called?

EDITORIAL LEARNING AID

Why is this answer correct?

The head of government of Brandenburg is the Minister-President, who is elected by the Landtag. A mayor heads a city or municipality, and the titles First Minister and Prime Minister are not customary in Germany.

Brandenburg's head of government: the Minister-President in Potsdam.

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