Which of the following embryos exhibits a parasitic mode of nutrition?

Blood flowing in the umbilical cord of a mammalian embryo is:

The persistence of corpus luteum during pregnancy is due to a hormone known as

Which of the following groups of hormones are produced in women only during pregnancy?

Match the items $A, B, C, D$ of table $'A'$ with the items in table $'B'$. Then,the correct pairing sequence of $A, B, C, D$ will be:
Table $'A'$ | Table $'B'$
$A.$ Cleavage | $1.$ Formation of $3$ germ layers
$B.$ Gastrulation | $2.$ Formation of embryo spinal cord
$C.$ Neurulation | $3.$ Results in formation of skeleton and muscles from mesoderm
$D.$ Organogenesis | $4.$ Pattern depends on the amount and distribution of yolk

What does the placenta consist of?