The Word "Countercurrent" Within "Countercurrent Multiplier" Refers to the Opposite

Multiple Choice

The word "countercurrent" within "countercurrent multiplier" refers to the opposite direction of flow of

A) sodium and potassium across the wall of the nephron.
B) tubular fluid within the ascending and descending limb of the nephron loop.
C) salts and water across the wall of the renal tubule.
D) tubular fluid in the proximal convoluted tubule and collecting tubule.