This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
Pansystolic murmur at apex with soft first hea sound is the key sign of which one of the following ? 
Select and explain. 
A. Aoic regurgitation, B. Mitral regurgitation, C. Ventricular septal defect, D. Atrial septal defect
B: Mitral regurgitation
Answer: B: Mitral regurgitation 
Explanation: MR : The regurgitant jet causes an apical systolic murmer.Pansystolic murmer with thrill, soft S1 AR: Early diastolic murmer ASD: Systolic flow murmer over pulmonary valve, diastolic flow murmer over tricuspid valve, wide fixed splitting of S2. VSD: Pansystolic murmer usually heated best at the left eternal edge Ref: Harrison 20th edition pg 1534