The figure below shows a human fetus within the uterus. Identify $P$ and $Q$.
$\quad\quad P \quad\quad\quad Q$

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.

The hormone responsible for the implantation of the embryo in the uterus and the formation of the placenta is:

At which stage of embryonic development is cell differentiation observed?

Placenta has an outer layer which is selectively permeable and hormone secreting which is known as

Foetal ejection reflex in human female is induced by