Question

Eutherians are characterized by
A. Hairy skin
B. Presence of teats
C. Ovoviviparity
D. True placentation

Answer 1

Hint: The Eutheria is one of the two mammalian clades with extant members that diverged in the Early Cretaceous or perhaps the Late Jurassic. All the placental mammals indigenous to Europe, Africa, Asia, the Americas, Australia, and Antarctica are the eutherians.

Complete answer: The eutheria is a taxon containing the placental mammals, such as the humans. This means that the foetus of the Eutherian is nourished during the process of gestation by a placenta. The eutherians are also viviparous, which means that the offspring are carried in the mother's womb until they are fully developed. The Eutherians is one of the two mammalian clades with extant members. All the eutherians possess a placenta and nourish their embryo during the embryonic development through the placenta only.
Therefore, the correct answer is option D.
Additional information:
The eutherians are distinguished from the non-eutherians by various phenotypic traits of the feet, ankles, jaws, and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals. This allows for the expansion of the abdomen during the period of pregnancy. One of the oldest-known eutherian species is the Juramaia sinensis. The Eutheria was named by Theodore Gill; in the year 1880, Thomas Henry Huxley defined it to encompass a more broadly defined group than the placental.

Note: The evolution of the placenta in all live-bearing animals offers females an advantage during the period of pregnancy. The animals with a placenta have smaller embryos that keep the females thin during the pregnancy period. This is the possible advantage that is of most importance during the early stages of pregnancy.