Which coat of arms belongs to the federal state of Brandenburg?

EDITORIAL LEARNING AID

Why is this answer correct?

Image 1 shows the Brandenburg coat of arms with the red eagle on a white field, the so-called Margrave's eagle. This symbol goes back to the Margraviate of Brandenburg and also appears on the state flag. Images 2 to 4 show the coats of arms of other federal states.

Red eagle on white: Brandenburg.

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