Correct Option: D

The heart is a hollow muscle that pumps blood throughout the blood vessels by repeated, rhythmic contractions. In mammals, the function of the right side of the heart (see right heart) is to collect deoxygenated blood, in the right atrium, from the body (via superior and inferior vena cavae) and pump it, through the tricuspid valve, via the right ventricle, into the lungs (pulmonary circulation) so that carbon dioxide can be dropped off and oxygen picked up (gas exchange). This happens through the passive process of diffusion.