This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
A new diuretic is being studied in human volunteers. Compared with placebo, the new drug increases urine volume, decreases urinary Ca2+, increases body pH, and decreases serum K+. If this new drug has a similar mechanism of action to an established diuretic, it probably 
Select and explain. 
A. blocks the NaCl cotransporter in the DCT, B. blocks aldosterone receptors in the CT, C. inhibits carbonic anhydrase in the PCT, D. inhibits the Na/K/2Cl cotransporter in the TAL
A: blocks the NaCl cotransporter in the DCT
Answer: A: blocks the NaCl cotransporter in the DCT 
Explanation: The effects described are typical of thiazide diuretics, which inhibit the Na/Cl cotransporter in the distal convoluted tubule. This action facilitates reabsorption of Ca2+, which is the basis for the use of thiazides in nephrolithiasis, and which can result in hypercalcemia. The increased load of Na+ in the collecting tubules leads to increased excretion of both K+ and Hi, so hypokalemia and alkalosis may occur.