Which one of the following is NOT correctly matched?

Detailed Solution:

The correct answer is “Vienna–Volga”.

Vienna - Volga is the incorrect pair. Vienna (Austria) is associated with the Danube River, not the Volga. The Volga River is primarily associated with Russia.

The other pairs are correctly matched:

Bonn (Germany) - Rhine
Cairo (Egypt) - Nile
New York - Hudson