You are answering a USMLE-style medical question. Question: A 64-year-old man presents to the clinic with easy fatigability and breathlessness when climbing stairs for the last 2 weeks. He also mentions that he occasionally has bouts of cough at night after about 2–3 hours of sleep which is relieved when he sits upright. He denies shortness of breath at rest, palpitations, and loss of consciousness. He has had hypertension for the last 20 years and is on antihypertensive medications. On physical examination, his temperature is 36.9°C (98.4°F), pulse is 104/min, blood pressure is 122/82 mm Hg, and respirations are 18/min. Chest auscultation reveals crackles over the lung bases bilaterally. Examination of his abdomen reveals mildly tender hepatomegaly. Laboratory investigation results include a hemoglobin of 14.8 g/dL (9.18 mmol/L) and an elevated serum B-type natriuretic peptide. His two-dimensional echocardiogram reveals an enlarged left atrium and an ejection fraction of 55%. Which of the following novel drugs is most likely to benefit the patient in addition to valsartan? Options: A) Etanercept B) Moxonidine C) Sacubitril D) Aliskiren Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.