The river begins in the andes mountains and flows eastward across south america to the atlantic ocean.

Amazon river

Explanation:

Amazon river -

It is the largest river present in the continent of South America ,

The river Amazon originates from the Andes mountains and flows eastwards all across the continent of south America and then at last enters the Atlantic Ocean .

The basin of the amazon river is the largest basin in the whole world .

hence , the correct answer according to the given information of the question is Amazon river .

Amazon River

Explanation:

The Amazon river origintaes from the Andes Mountains of western South America. It flows east from there to the Atlantic Ocean. Most of the huge river and its many tributaries are in the country of Brazil