Match the description of the murmur to the valvular lesion.

There is a narrowing of the orifice of the valve. A low pitched, mid-di- astolic murmur is heard. There is often a louder than normal first sound as the valve is shut more forcefully than normal.

a. Aortic regurgitation
b. Aortic stenosis
c. Mitral regurgitation
d. Mitral stenosis