Which of the following is a district in North Rhine-Westphalia?

EDITORIAL LEARNING AID

Why is this answer correct?

The Rhein-Sieg-Kreis lies between Bonn and Cologne and is a district in North Rhine-Westphalia. Ammerland belongs to Lower Saxony, Nordfriesland to Schleswig-Holstein and the Vogtlandkreis to Saxony.

Rhein-Sieg district: between Bonn and Cologne, so in NRW.

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