Which is the longest river in South America?

Which is the longest river in South America?

جنوبی امریکہ کا سب سے لمبا دریا کون سا ہے؟
Explanation

The Amazon River in South America is the largest river by discharge volume of water in the world,

longest or second-longest river system in the world,

a title which is disputed with the Nile. 

Source: Mantaro River

Length: 6,400 km

Mouth: Atlantic Ocean

By far the largest system is formed by the Amazon River,

which stretches some 4,000 miles  across equatorial South America.