The correct option is
D Blood fills the heart
During atrial diastole, deoxygenated blood enters the right atrium through superior and inferior venae cavae and oxygenated blood enters the left atrium through the pulmonary veins. During ventricular diastole, oxygenated blood enters from left atrium to left ventricle and deoxygenated blood enters from the right atrium to the right ventricle.
So, the correct answer is option D.