Quick Quiz: Nouns Score: Change category, Flip order Reset Incorrect! Try again. Noun: euphrates Your choice? a river in southwestern Asia; flows into the Persian Gulf; was important in the development of several great civilizations in ancient Mesopotamia Eurasian toad with variable chiefly green coloring assimilation into European culture   (Noun: europeanization) a bivalent and trivalent metallic element of the rare earth group