B. The superior vena cava in the adult is derived from structure of the embryo? I 1. right common cardinal and right precardinal veins 2. left common cardinal and left precardinal veins 3. Superior mesenteric vein 4. Inferior mesenteric vein C. The embryonic organ most closely associated with the appearance of ductus venosus is the: 1. Kidney 2. Liver 3. Caudal loop of the colon 4. Gall bladder