Question: The island for which Ferdinand Avenarius is first popularizer belongs to which islands?
Sentence (from "Sylt"): Sylt (] ; Danish: "Sild" ; Söl'ring North Frisian: "Söl") is an island in northern Germany, part of Nordfriesland district, Schleswig-Holstein, and well known for the distinctive shape of its shoreline.
Relevant evidence: Yes