The vessel that shunts fetal blood right to left between the pulmonary artery and aorta is the

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During fetal life the lungs don’t participate in gas exchange, so blood must bypass them. The vessel that does this by connecting the main pulmonary artery to the aorta allows blood to flow from the pulmonary circulation directly into the systemic circulation. Because the pulmonary artery is on the right side of the circulation and the aorta on the left, the flow is a right-to-left shunt. This ductus arteriosus is essential for routing oxygenated blood to the body before birth and it closes after birth, becoming the ligamentum arteriosum.

The other options don’t fit this route: the foramen ovale shunts blood from right atrium to left atrium, not between the pulmonary artery and aorta; the ductus venosus bypasses the liver in the umbilical venous system, not the lungs; and the ligamentum arteriosum is what the ductus arteriosus becomes after birth, not a fetal shunt.