Task: Question Answering
Input (English): Question: A 82-year-old hypertensive woman on treatment with atenolol, hydrochlorothiazide and digoxin. He goes to the emergency room for atrial fibrillation and is administered verapamil i.v. Complete atrioventricular block is evidenced in ECG. What is the most likely cause of this clinical situation? 
 Options:  <1> Digitalis intoxication by pharmacokinetic interaction by verapamil. <2> Hypokalemia due to the administration of thiazide and digoxin. <3> Pharmacodynamic interaction of beta-blocker, digoxin and verapamil. <4> Hypotensive effect of the thiazide diuretic. <5> Cardiac arrhythmia due to verapamil.
Output (English): 3