What is the head of government of the city-state of Berlin called?

EDITORIAL LEARNING AID

Why is this answer correct?

Berlin's head of government is called the Governing Mayor; he leads the Senate, the state government. A Lord Mayor heads Munich, for example, the title President of the Senate belongs to Bremen, and Minister-President is the title used in the area states.

Berlin: Governing Mayor; Bremen: President of the Senate.

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