Relaxin (a hormone) is secreted by

The diagram shows one of the human embryonic developmental stages. What do $A$ and $B$ indicate?

Match the hormone with its site of production:

Hormone	Site of production
$A$. $hCG$ and $hPL$	$(ii)$ Placenta
$B$. Progesterone	$(iii)$ Corpus luteum
$C$. Androgens	$(iv)$ Leydig cells
$D$. Relaxin	$(i)$ Ovary

If the ovaries are removed in the fourth month of pregnancy,what will happen?

Thalidomide is a non-barbiturate sedative drug which was given to pregnant women. Its use was withdrawn in $1961$ because it resulted in phocomelia. This condition illustrates:

During embryonic development,which germ layer gives rise to the endoskeleton and muscles?