Question

In mammals, the chorion and the allantois together form

• A. Placenta
• B. Endometrium
• C. Uterus
• D. Yolk sac

Answer 1

Answer: (A)

Placenta

Chorion is a layer of the extraembryonic membrane which forms the embryonic portion of the placenta. It provides nutrition to the developing embryo.
The allantois is the sac-like extraembryonic membrane that removes the waste from the embryo. As the embryo grows the allantois also grows and presses against the chorion. This allows the allantois to exchange oxygen and carbon dioxide with the air outside the eggshell.

So, the correct answer is option A.