Rivers 'Ob' and 'Amur' are associated with:

The correct answer is Option (4) → Siberia

The Ob and the Amur are two of the great rivers of Siberia, the vast Asian part of Russia.

• Ob: rises in the Altai Mountains and flows north across the West Siberian Plain into the Gulf of Ob, an arm of the Arctic Ocean.

• Amur: flows east through the Russian Far East, forming a long stretch of the Russia–China border, and enters the Pacific side through the Strait of Tartary.