The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Which heart sound indicates stiffness of ventricular wall   (A) S1   (B) S2   (C) S3   (D) S4
['(D) S4 <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) S1 \n (B) S2 \n (C) S3 \n (D) S4 <> possible answers', '  Which heart sound indicates stiffness of ventricular wall <> context@']