Question Detail
Question
In mammals, the extra-embryonic structure is composed of
Correct Answer
Option A is the correct answer.
Detailed Explanation
In mammals, the extraembryonic structures include the chorioallantois (formed by fusion of the chorion and allantois, which becomes the placenta in eutherians) and the trophoblast (the outer layer of the blastocyst that contributes to the chorion and mediates implantation). While amnion, yolk sac, and allantois are also extraembryonic, the most characteristic mammalian extraembryonic structures are the trophoblast and the chorioallantoic placenta.
Hint
Consider the unique structures that are involved in implantation and placentation in mammals.