<prompt>  A 56-year-old man presents to his internist with jaundice. The patient is receiving no medication and his only symptomatic complaint is mild fatigue over the past 2 months. Physical examination is remarkable only for the presence of scleral icterus. The patient has no significant past medical history. Analysis of serum chemistry reveals the following- SGOT : 0.58 microkatL 35UL SGPT : 0.58 microkatL 35UL, Total bilirubin: 91.7 micron molL 7mgdL Direct Bilirubin:85.5 micron molL 5 mgdL Alkaline phosphatase : 12 micron katL720 UL Which of the following is the next most appropriate diagnostic step?UltrasoundLiver biopsyReview of peripheral blood smearEndoscopic retrograde cholangiopan creatography ERCP 