The Countercurrent Mechanism in the Nephron

Multiple Choice

The countercurrent mechanism in the nephron

A) creates a highly concentrated interstitial fluid so that urine can be concentrated by the collecting ducts when they are permeable to water.
B) is a method to move sodium to control its concentration.
C) keeps the volume of water lost in the urine relatively constant.
D) keeps interstitial fluid hydrated to maintain blood pressure.