This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Free water clearance is positive when urine is 
Select and explain. 
A. Dilute, B. Concentrate, C. Isotonic, D. Any of the above
A: Dilute
Answer: A: Dilute 
Explanation: Ans. is 'a' i.e., Dilute(Ref: Principles of Medical Physiology p' 39IlKidney excretes some solutes in the urine daily.The volume of tater in urine, excreted per unit time in excess of thot required to excrete the contained solutes is-osmotically with plasma.Free water clearance is positive in dilute urine, negative where concentrated urine is passed and zero when isotonic urine is passed.