B

Complete obstruction of the common bile duct prevents any conjugated bilirubin from reaching the gut, so serum bilirubin can climb to very high levels (often > 30 mg/dL and occasionally around 40 mg/dL). Malignant or partial obstructions usually allow some trickle flow and produce lower values, while renal failure does not elevate bilirubin and liver failure causes hepatocellular—not obstructive—jaundice [Egbert 1983, PMID 6847365; Lapis 1978, PMID 666189].