I would go with mathmatical formula because of physics and what not but I'm not completely sure so if you have a different possible answer you think would be better, go with that :)
It receives blood from the whole body. Blood from the lungs enters the heart through the pulmonary vein into the left atrium. ... - Has ventricles that has thicker walls thus more muscular than auricles generating higher pressure to pump blood over long distances.
D.
Viruses are not considered to be living organisms but they can function inside living cells and multiply by using things in the cells. They can cause diseases in living organism and studying them is important in the medical field.