Answer:
Structure. The IVC is formed by the joining of the left and right common iliac veins and brings collected blood into the right atrium of the heart. It also joins with the azygos vein (which runs on the right side of the vertebral column) and venous plexuses next to the spinal cord.
Source: common iliac vein; lumbar veins;
I believe the correct answer would be metabolism. This comprises all of the reactions inside organisms that allows them to sustain life. There are two categories of such namely, anabolism and catabolism. Hope this answers the question.