Which of the following substances can pass through the placenta from the mother into foetus
Proteins
Viruses of small pox
$WBCs$
$RBCs$
Type of cleavage found in mammals is
The cyclic period of sexual activity in non-human female mammals is called
The breakage of the membrane surrounding the acrosome in a mammalian sperm is
The respiratory function of embryo is performed by
Which of the following hormones is not a secretary product of human placenta?