The artery is defined as the blood vessel that carries blood away from the heart.
The largest artery is the aorta that carries oxygenated blood from the left ventricle to the entire blood.
The veins are defined as blood vessels that carry blood towards the heart.
The largest vein in the human body is vena cava, that collects deoxygenated blood from the body and brings it to the heart.
Final Answer:
The largest (a) Artery is aorta and (b) Vein is vena cava in our body.