What Does NOT Contribute to the Establishment of a Vertical

Multiple Choice

What does NOT contribute to the establishment of a vertical osmotic gradient in the interstitial fluid of the renal medulla?

A) the renin-angiotensin-aldosterone system
B) countercurrent multiplication in the long loops of Henle of juxtamedullary nephrons
C) urea recycling between the late portion of the collecting tubule and the long loops of Henle
D) active transportation of sodium out of ascending limb of the loop of Henle