A premise is a statement, usually put forth as part of a logical argument, that will be presumed true for the purposes of that argument. Naturally, the accuracy of a given conclusion is partially dependent on the accuracy of the chosen premises.
... river in the world by volume, the Parana[?] with its impressive Iguaçu[?] falls, the Rio Negro, São Francisco[?], Xingu, Madeira and the Tapajós[?] rivers.
Situated ...