Question

The eutherian placenta is derived from
A.Yolk sac
B.Amnion
C.Allantois
D.Chorion allantois

Answer 1

Hint: The class mammalian is divided into subclasses : Prototheria and theria. The subclass theria is divided into two infraclasses: Metatheria and Eutheria

Complete answer:
The subclass theria is divided into two infraclasses.: Metatheria and Eutheria
The eutherians occur all over the world. The anal and urogenital apertures have separate sphincters. Placenta is well developed
The young have a prolonged intrauterine development and are born in an advanced stage.
The eutherians are called placental mammals on account of having a typical placenta.
The chorion is the outermost embryonic portion of the placenta and the allantois sac like extraembryonic membrane, that removes the waste from the embryo by the fusion of the allantois and chorion

So, the correct answer is option D. Chorion allantois
Additional information:
The placental mammals may be arranged in four evolutionary lines-
-Insectivorous line : include the primitive insect eating placental and the groups arising from it,such as bats and primates
-Rodents and rabbits: they are gnawing placentals.
-Whales, dolphins and porpoises. These are aquatic placental.
-Elephants, carnivores and ungulates. These are gregarious placental

Note:
Theria are modern young producing (viviparous) mammals. They lack cloaca therefore, digestive tract and urogenital ducts open directly to the exterior by separate apertures. Eggs are with little yolk and no shell. They develop in the uterus and the living one is delivered.