The correct answer is 2 - hypokalemia. Some medications, including diuretics, can increase potassium excretion by the kidneys, leading to hypokalemia. Severe hypokalemia can be life-threatening, as it can lead to serious cardiac arrhythmias and cardiac arrest.
Hyponatremia (not hypernatremia, which causes thirst initially) can also be caused by diuretics and is characterized by an abnormally low sodium level in the blood and can lead to life-threatening complications, such as cerebral edema.