Answer the following question given this paragraph: The four-chambered mammalian heart can pump blood in two different directions. The right side of the heart pumps blood to the lungs to pick up oxygen. The left side of the heart pumps blood containing oxygen to the rest of the body. Because of the dual pumping action of the heart, all of the blood going to body cells is rich in oxygen. Q: How many chambers does a mammalian heart have? Choices: - one - five - three - four A:
Answer:
four