Q. A 53-year-old man comes for a pre-employment medical examination. The patient has no significant medical history. He never smokes; however, he drinks alcohol socially. His vital signs are BP: 160/100 mmHg, HR: 72 bpm, respiratory rate 12/min, and temperature: 37.0 degrees Celsius. Chest auscultation reveals no abnormality. Cardiac auscultation reveals a systolic ejection murmur over the aortic area radiating to the carotid. No additional cardiac sounds are heard. Which of the following is the most common cause of this patient's murmur?