In what order does blood flow through the heart?

The correct sequence of blood flow through the heart, as represented in the answer provided, highlights the fundamental pathway that blood takes during circulation. Blood returns from the body to the heart via the superior and inferior vena cavae, entering the right atrium. From the right atrium, blood flows into the right ventricle, which then pumps it to the lungs through the pulmonary arteries. In the lungs, blood exchanges carbon dioxide for oxygen before returning to the heart via the pulmonary veins, entering the left atrium.

This pathway is essential for understanding both the pulmonary and systemic circuits of circulation. The movement from the right atrium to the right ventricle, then to the lungs for oxygenation, is critical in maintaining an efficient cardiovascular system. Once the blood becomes oxygen-rich in the lungs, it returns to the left side of the heart, where it can then be distributed throughout the body. This information establishes B as the correct answer, reflecting the accurate trajectory of blood flow through the heart and lungs.