A 68-year-old man with CKD stage 3b (eGFR 35 mL/min/1.73 m²) has serum potassium 6.2 mmol/L, peaked T waves on ECG but is alert and haemodynamically stable. According to standard emergency management principles, what is the most urgent next step?AAdminister intravenous calcium gluconateBStart oral sodium polystyrene sulfonate onlyCRestrict dietary potassium and recheck in the morningDGive loop diuretic aloneEArrange outpatient nephrology reviewCheck my answer