The force of blood flowing through the __________ keeps it firm.
A) amnion
B) umbilical cord
C) yolk sac
D) embryonic disk
Question 2
The placenta __________.
A) forms in the second trimester of pregnancy
B) encloses the developing organism in amniotic fluid
C) contains one large vein that delivers nutrients to the embryo
D) delivers food and oxygen to the developing organism