उत्तर : 2. "वोल्गा"
व्याख्या :

Volga River is a river of Europe. It falls into the Caspian Sea. Volga River is the longest river of Europe and European Russia and an important waterway of Russia. Originating from a source situated at a height of 665 feet on the Valdai Mountain, this river falls into the Caspian Sea through a winding route of 1,300 miles and forms a delta at the mouth.