Answer:
Adjacent to the yolk sac
Step-by-step explanation:
Chorionic villi are microscopic and fingerlike projections found near the placenta which contain capillaries, increase surface area of blood that allow blood to flow and transfer nutrients from the mother to the fetus. The chorionic villi is adjacent to the yolk sac because it developed from the yolk sac, villi can extend and contact maternal blood vessels thereby nourishing the embryo and transfering nutrients from the mother to the fetus.