In humans,the placenta is formed by which of the following?

Given below are two statements with respect to gastrulation.
$Statement-I$: Root of amniotic cavity is lined by amniogenic cells, which divides to form chorion.
$Statement-II$: Chorion is an embryonic membrane that participates in development of the embryo.
Choose the most appropriate answer from the options given below.

In the mammalian embryo,the excretory material is stored in:

Gastrula has a pore which is known as . . . . . .

Chorion is composed of

In the simplest type of placenta,the foetal blood is separated from the maternal blood by six barriers. How many barriers are lost in the human placenta?