The correct answer is option 4, Volga. The Volga River is the longest river in Europe, spanning a length of about 3,530 kilometers. It flows through central Russia and is an important transportation route, connecting Moscow and the Caspian Sea.
Let`s now look at the other options:
- Option 1, Rhine: The Rhine River is one of the longest rivers in Europe, but it is not the longest.
- Option 2, Rhone: The Rhone River is the second longest river in France, but it is not the longest river in Europe.
- Option 3, Danube: The Danube River is the second longest river in Europe, but it is not the longest.
Therefore, the correct answer is option 4, Volga.