Task: Question Answering
Input (English): Question: In patients with digitalized congestive heart failure, when administering a diuretic, it must necessarily be: 
 Options:  <1> A loop diuretic or high ceiling. <2> A thiazide. <3> An osmotic diuretic. <4> A potassium-sparing diuretic. <5> A diuretic carbonic anhydrase inhibitor.
Output (English): 4