An asymptomatic 47-year-old woman comes to the physician for a routine health maintenance examination. She has no history of rheumatic fever. She takes no medications. Her pulse is 70./min. and blood pressure is l50./`60 mm Hg. A grade 2/`6 decrescendo murmur that begins after S2 is heard at the left sternal border. Which ofthe following is the most likely diagnosis?
A) Aortic valve insufficiency
B) Aortic valve stenosis
C) mtral valve regurgitation
D) mitral valve stenosis
E) Tricuspid valve regurgitation