Select the correct statement(s) about the circulatory system of birds and mammals:

A. They exhibit complete double circulation.

B. Deoxygenated blood passes through the right side of the heart.

C. Only oxygenated blood passes through the ventricles.

D. The ventricles pump mixed blood.

In birds and mammals, oxygenated and deoxygenated blood received by the left and right atria respectively passes on to the ventricles of the same sides. The ventricles pump it out without any mixing up, i.e., two separate circulatory pathways are present in these organisms, hence, these animals have double circulation. 

The left ventricle pumps oxygenated blood while the right ventricle pumps deoxygenated blood.

The ventricle pumps mixed blood in amphibians and reptiles (incomplete double circulation).