The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Which of the following vitamin is synthesized in vivo, in the body by humans?   (A) Niacin   (B) Pantothenic acid   (C) Cyanocobalamin   (D) Folic acid
['(A) Niacin <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Niacin \n (B) Pantothenic acid \n (C) Cyanocobalamin \n (D) Folic acid <> possible answers', '  Which of the following vitamin is synthesized in vivo, in the body by humans? <> context@']