Aortic Regurgitation (AR) is caused by various conditions affecting the aortic valve and root.
Congenital causes like bicuspid aortic valve and myxomatous degeneration (prolapse) can weaken valve closure and lead to AR.
Endocarditis and Rheumatic fever are common acquired causes that damage valve leaflets.
Syphilis, especially tertiary syphilis, can cause aortic root dilatation leading to AR.
Ankylosing spondylitis is a chronic inflammatory disease that can also cause aortic root inflammation and regurgitation.
Therefore, all four options listed (A, B, C, D) are valid causes of Aortic Regurgitation.