Answer: B. right atrium --> right ventricle --> left atrium --> left ventricle
Explanation: Deoxygenated blood enters the superior vena cava and inferior vena cava and collects it on the right atrium. It is then pumped up through a valve and enters the right ventricle. Then it is transported by the pulmonary artery to the lungs to become oxygen rich blood. From the lungs oxygenated blood enters into the pulmonary vein and back into the heart and goes inside the left atrium. The blood is pumped again through a valve going to the left ventricle and transported to the body through the aorta which distributes oxygen rich blood.
