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: Medicine
In a woman with polyuria of 6L/day, which are the 2 most important investigations to be done - 
Select and explain. 
A. Plasma and urine osmolality, B. Water loading, C. Water deprivation test, D. Plasma osmolality
C: Water deprivation test
Answer: C: Water deprivation test 
Explanation: fluid deprivation test to differentiate which type of DI. If it is not significant administration of desmopressin required