The ductus arteriosus allows fetal blood to move from the

The ductus arteriosus allows fetal blood to move from the pulmonary trunk into the aorta. The ductus venosus on the other hand is a fetal vessel that transports blood from the umbilical vein to the inferior venacava. Ductus arteriosus is a blood vessel connecting the main pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled non-functioning lungs.

The answer is joseph is observing the colour of the reaction mixture to see whether proteins are present in the given solution.