The blood enters the right atrium (RA) of the heart through the superior and inferior vena cava, passes through the tricuspid valve (between the right atrium and the right ventricle) to reach the right ventricle (RV). The blood from RV is then pumped through the pulmonary artery to the lungs. In the lungs the oxygenation of the blood occurs and then through the pulmonary vein the oxygenated blood enters the left atrium (LA). The blood then enters the left ventricle (LV) (through the bicuspid valve) and is then pumped through the aorta to rest of the body. Thus, the correct diagrammatic representation is seen in option A.