easy one but high yield - darkhorse

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A 45-year-old man is brought to the emergency department after fainting while walking his dog. He denies a history of chest pain or prior syncope. His past medical history is significant for a cardiac murmur known since childhood. He does not smoke, and denies any recreational drug use. His temperature is 37 C (98.6 F), blood pressure is 128/78 mm Hg, pulse is 87 /min and regular, and respiratory rate is 18/min. He has a prominent apical impulse and a II/VI, late peaking murmur at the right upper sternal border that decreases in intensity with a Valsalva maneuver. An electrocardiogram shows large S waves in leads V1 and V2, and large R waves in leads V4 through V6, with ST depressions in leads V5 and V6. The most likely diagnosis is

A. aortic stenosis
B. idiopathic hypertrophic subaortic stenosis (hypertrophic cardiomyopathy)
C. pericarditis
D. pulmonary embolism
E. pulmonary hypertension