Which of these is a district (Landkreis) in Schleswig-Holstein?

EDITORIAL LEARNING AID

Why is this answer correct?

The district of Nordfriesland lies on the North Sea coast of Schleswig-Holstein and includes Sylt, Föhr and Amrum, among others. Ammerland belongs to Lower Saxony, the Mecklenburgische Seenplatte to Mecklenburg-Western Pomerania and the Rhein-Sieg-Kreis to North Rhine-Westphalia.

Nordfriesland: the district on the North Sea, with Sylt.

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