The answer is the last one
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.
Answer:
the cell theory is:
1. all organisms are made of cells
2. all cells are produced by other living cells
3. the cell is the most basic unit of life