Blood flowing in umbilical cord is
$50\%$ maternal and $50\%$ foetal
$100\%$ foetal
$100\%$ maternal
$75\%$ maternal and $25\%$ foetal
Tertiary egg membranes are lacking in mammals with the exception of the
During the fourth and sixth cleavage of the zygote
Onset of menstruation is due to
External stimulus which induces cleavage in an unfertilized ovum is called
The central nervous system develops as a result of