Which Human Extraembryonic Membrane Forms the Blood Vessels of the Umbilical

Question

Which human extraembryonic membrane forms the blood vessels of the umbilical cord?  
A) Amnion
B) Yolk sac
C) Chorion
D) Allantois
E) Protein coat

Accepted Answer

The allantois is involved in early fluid exchange between the embryo and the yolk sac. In mammals, including humans, the allantois eventually forms the blood vessels of the umbilical cord, connecting the fetus to the placenta.