Which of the follwoing is TRUE about free water clearance?

"Free water clearance" (CH2O) is the difference between the urine volume and the clearance of osmoles (COsm). The excretion or retention of electrolyte-free water by the kidney is modulated by circulating vasopressin (ADH). ADH acts on renal V2-type receptors in the thick ascending limb of Henle and principal cells of the collecting duct (CD), increasing cyclic adenosine monophosphate (AMP) and activating protein kinase A (PKA)-dependent phosphorylation of multiple transpo proteins. Ref: Mount D.B. (2012). Chapter 45. Fluid and Electrolyte Disturbances. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.