Final answer:
The largest and most important river system in South America is the Amazon River. It is the world's largest river by volume and plays a crucial role in the region's ecosystem.
Step-by-step explanation:
The largest and most important river system in South America is the Amazon River. Spanning across several countries including Brazil, Peru, Colombia, and more, it is the world's largest river by volume and carries more water than any other river. The Amazon River plays a crucial role in the region's ecosystem, supporting a diverse range of plant and animal species and serving as an important transportation route.
Learn more about South America's largest river system