Which of the following statements violates the cell theory? a) mitosis produces new cells identical to the parent cell that divided to make them. b) viruses are not considered to be living organisms, because they are smaller than a cell. c) though humans are one organism, they are composed of about 100 trillion individual cells. d) some scientists believe that prions, tiny proteins much smaller than a cell, that can replicate themselves, may be living organisms.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.