What are the heads of government of most federal states in Germany called?

EDITORIAL LEARNING AID

Why is this answer correct?

In 13 of the 16 federal states the head of government is called Minister-President. Berlin, Hamburg and Bremen use their own titles (Governing Mayor, First Mayor, President of the Senate); senators there are members of the government, and "First Minister" or "Prime Minister" are not German titles.

Usually "Minister-President" — city-states use other titles.

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