The proximity between Henle's loop and vasa-recta as well as the counter-current in them help in maintaining an ...$A$... in molarity towards the inner medullary interstitium,i.e.,from ...$B$... $mOsmol \ L^{-1}$ in the cortex to about ...$C$... $mOsmol \ L^{-1}$ in the inner medulla. Here $A$,$B$,and $C$ refer to:

• A
  $A-$increasing,$B-500, C-800$
• B
  $A-$decreasing,$B-300, C-1200$
• C
  $A-$decreasing,$B-1200, C-300$
• D
  $A-$increasing,$B-300, C-1200$