Blood enters the heart because muscles of the

Options

A. Atrium contracts
B. Atrium relaxes
C. Ventricle relaxes
D. Ventricle contracts

Answer

B

Explanation

Blood enters into the heart due to pressure difference between ‘pulmonary artery and right atrium’ and ‘pulmonary vein and left atrium’. It moves from high pressure to low pressure by increasing the volume of atrium during diastole.