This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
The following Thiazide diuretic is active if the GFR is 30-40 mm Hg 
Select and explain. 
A. Metolazone, B. Benzthiazide, C. Chlorothiazide, D. Chlohalidone
A: Metolazone
Answer: A: Metolazone 
Explanation: Although most thiazide diuretics lose their effectiveness in renal failure, metolazone remains active even when the glomerular filtration rate (GFR) is below 30-40 mL/min (moderate renal failure). This gives it a considerable advantage over other thiazide diuretics, since renal and hea failure often coexist and contribute to fluid retention(Refer: K. D. Tripathi&;s Essentials of Medical Pharmacology, 7th edition, pg no: 583)