Ans. is 'a' i.e., Common iliac vein o Derivatives of anterior cardinal venous system are1. Superior vena cava (SVC) is derived from (i) right anterior cardinal vein (proximal to brachiocephalic anastomosis), and (ii) right common cardinal vein.2. Right brachiocephalic vein is formed by right anterior cardinal vein (part which lies between right 7th cervical intersegmental vein and brachiocephalic anastomosis).3. Left brachiocephalic vein is formed by brachiocephalic anastomosis (between two anterior cardinal veins).4. Subclavian veins are formed by 7th cervical intersegmental vein.5. Internal jugular veins are formed by anterior cardinal veins (part which lies cranial to their junction with 7 cervical intersegmental vein).6. External jugular veins arise as secondary channel (not derived from anterior cardinal veins).7. Left superior intercostal vein is formed by regressed part of left anterior cardinal vein (caudal to transverse anastomosis) and cranial part of posterior cardinal vein.8. Verteral veins are developed by longitudinal anastomosis between C1 to C7 intersegmental veins and intercostal veins.o Derivatives of posterior cardinal veins, subcardinal veins and supracardinal veins are :1. Inferior vena cava is derived from :-a) Hepatic segment of IVC is derived from (i) right hepatocardiac channel, and (ii) anastomotic channel between subcardinal vein and right hepatocardiac channel.b) Renal segment of IVC is derived from right subcardinal vein. This part receives both renal and suprarenal veins.c) Post renal segment of IVC (major part of IVC) is formed by (i) anastomosis between right supracardinal and subcardinal veins, (ii) right supracardinal vein (lower part), and (iii) right posterior cardinal vein (lowest part).2. Gonadal veins develop from subcardinal veins (distal part below inter-subcardinal or renal anastomosis).3. Suprarenal veins develop from subcardinal veins (proximal part above inter-subcardinal or renal anastomosis).4. Right common iliac vein is derived from right posterior cardinal vein (most caudal part).5. Left common iliac vein develops from transverse anastomosis between lower end of posterior cardinal veins.6. Right renal vein is a mesonephric vein that drains into renal segment of IVC (which is derived from upper part of right subcardinal vein).7. Left renal vein develops from three sources : (i) mesonephric vein (drain into left subcardinal vein), (ii) left subcardinal vein (small part), and (ii) pre-aortic intersubcardinal anastomosis.