Final answer:
The middle hepatic vein is responsible for draining the systemic blood from the liver into the inferior vena cava.
Step-by-step explanation:
The vein that drains the liver is the hepatic vein. The liver receives its blood supply from two sources: the hepatic artery and the hepatic portal vein. The liver processes this blood and drains the systemic blood via the right, left, and middle hepatic veins, which then flows into the inferior vena cava. Therefore, the correct answer to which vein will drain the liver is A) middle hepatic vein.