us-abim MCQ (SBA): Heart Failure (HFrEF)

A 58-year-old with HFrEF (LVEF 30%, NYHA II) is on lisinopril and metoprolol succinate. BP 124/74 mm Hg, K+ 4.6 mEq/L, eGFR 65 mL/min/1.73 m². Which additional medication class should be part of guideline-directed medical therapy to reduce mortality and HF hospitalization regardless of diabetes status?