Concept:The mammalian heart is the pump of circulation, and its main pumping chamber for the whole body is the left ventricle.
Explanation:The left ventricle receives oxygenated blood from the left atrium.
It has a very thick muscular wall, enabling it to generate high pressure.
When it contracts, it forces this oxygen-rich blood through the aortic valve and into the aorta.
From the aorta, the blood is distributed through arteries to all body tissues.
The right auricle only receives returning deoxygenated blood, so it is not the main pumping chamber.
Veins carry blood back to the heart, and arteries carry blood away, but neither vessel pumps blood.
Therefore, the left ventricle is the primary structure responsible for pumping blood around the mammalian circulatory system.
Answer:D. left ventricle