Explanation:

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The Paraguay River is a major river in south-central South America, running through Brazil, Bolivia, Paraguay and Argentina.

The Congo River, formerly known as the Zaire River during the dictatorship of Mobutu Sese Seko, is the second longest river in Africa, shorter only than the Nile, as well as the second largest river in the world by discharge volume, following only the Amazon.

The Volga is the longest river in Europe with 3,531 km length and a catchment area of 1,360,000 km². It is also Europe's largest river in terms of discharge and drainage basin. The river flows through Central Russia and into the Caspian Sea, and is widely regarded as the national river of Russia.

The Ob River, also Ob', is a major river in western Siberia, Russia, and is the world's seventh-longest river. It forms at the confluence of the Biya and Katun Rivers which have their origins in the Altay Mountains.