Welcher Fluss prägt Niederösterreich am stärksten?

Why this is the correct answer

Lower Austria surrounds the capital Vienna and is shaped more than any other Austrian state by the Danube, which flows nearly 200 kilometres through it from west to east. Many of Lower Austria's most important towns, monasteries and wine regions — including the Wachau and the Nibelungengau — developed along the Danube's banks. Rivers like the Mur and Salzach belong to entirely different regions of Austria.