Among the given options, the correct answer is option 1 - Amazon. The Amazon River is the longest river in the world, stretching approximately 6,400 kilometers (4,000 miles) from its source in the Andes Mountains of Peru to its mouth in the Atlantic Ocean in Brazil.

Option 2 - Amur, is a river in eastern Asia that flows through China and Russia, but it is not the longest river in the world.

Option 3 - Congo, is the second longest river in Africa, but it is not the longest river in the world.

Option 4 - Volga, is the longest river in Europe, but it is not the longest river in the world.

It is important to note that while the Amazon River is the longest in terms of length, there are other rivers that are recognized as the longest in other categories such as volume of water flow or drainage basin size.