Water separates all countries of northern europe from the rest of europe except

denmark
finland
norway
sweden

Denmark

Explanation:

Denmark is a sovereign country member of the European Union located in northern Europe. It is the southernmost of the Nordic countries and also the smallest. Officially, the Kingdom of Denmark, is a community composed of three autonomous parts, Denmark itself and its two overseas territories or dependent territories, Greenland and the Faroe Islands. Its capital and most populous city is Copenhagen, which is located on the island of Zealand.

Denmark is part of Scandinavia and only has a land border with Germany, although since 1999 it has been linked to Sweden by road and rail, via the Øresund bridge. The Danish territory is composed of the Jutland peninsula (Jylland) and 407 islands of which 79 are inhabited (2009). Denmark has 7314 km of coasts and is completely surrounded by the North Sea and the Baltic Sea, with the exception of Jutland, which links it to the European continent. The main Danish islands are Zealand (Sjælland), Fyn (Fyn), Vendsyssel-Thy, Lolandia and Bornholm, the furthest from the Danish archipelago. This position has given Denmark, historically, control over access to the Baltic Sea.

the answer is a, salt plain