cardiology with increasing dyspnoea or exertion and a systolic murmur. slow rising pulse.. Calcification of the aortic valve

An 82-year-old man is referred to cardiology by his GP with increasing dyspnoea or exertion and a systolic murmur. Examination demonstrates a blood pressure of 100/80 mmHg and a slow rising pulse. What is the most likely cause of his underlying condition?
A.A Bicuspid aortic valve
B.A Ventricular septal defect
C.A Post rheumatic fever
D.A Calcification of the aortic valve***
E.A Hypertrophic obstructive cardiomyopathy.