Question

Extra-embryonic membranes of the mammalian embryo are derived from
A. Inner cell mass
B. Trophoblast
C. Formative cells
D. Follicle cells

Answer 1

Hint:
The life inside the womb is limited in the aspect of the nutrition provided or safety. So the special is there for nourishment and protection throughout the period. From the implantation to the delivery, these cells take care of every process. Division of cells to form every limb makes the gestation period.

Complete answer:
What are the extraembryonic membranes? The embryonic layers made during the development of the embryo to protect and nourish it are extra-embryonic layers. There are 4 types of membrane- amnion, chorion, allantois and yolk sac.
Option A: Inner cell mass: These are the cells which will form the special features of the fetus. It is also called embryoblast. These cells will convert into a completed embryo.
Option B: Trophoblast: It is present after 4 days of fertilization. It will provide nutrition and protection to the embryo. It forms the outer of the blastocyst. They form the extra-embryonic layers. They do not form the fetus but are just for protection and nourishment, so they form placenta and membranes.
Option C: Formative cell: The embryo cell is the formative cell which can exist independently. It is the structural and functional unit of cellular organisms.it forms tissues in the higher organisms.
Option D: Follicle cell: the cells that surround the oocyte in the follicle are follicle cells.they are triggered by the levels of gonadotropins. They protect the egg. They produce thyroid hormones thyroxine(${T_4}$) and triiodothyronine(${T_3}$).

So the answer is option B: Trophoblast.

Note:
Fertilization of egg and sperm produces the embryo. A zygote is the first cell of the body. It is less than 1mm in diameter. Till the eighth week, a zygote is called an embryo, after then it is called a foetus. The study of an embryo is embryogenesis. It is a multicellular diploid cell.