Which of the following is the most likely cause of the systolic murmur heard in Mr. Santos?

Mr. Santos, a 55-year-old male, visits the clinic for a routine check-up. He has a history of hypertension and is currently taking antihypertensive medications. He reports occasional dizziness and shortness of breath. Upon assessment, the nurse notes elevated blood pressure and Auscultates a systolic murmur over the aortic area.