1) According to the passage , why is the Rio Grande so important? A. It is a source of drinking water for most of the United States. B. It is the border of Texas and Mexico. C. It is the longest river system in the United States. D. It is known by two different names. 2) In paragraph 3, the author most likely writes that "downward is the best way of describ A. prove that the Rio Grande's water levels have gone down recently B. argue that the Rio Grande has changed shape over the years C. highlight the fact that the Rio Grande flows south and from high elevations D. explain why the Rio Grande is known as the Rio Bravo down in Mexico