Implantation is the process of

When the cleavage furrow extends from the animal pole to the vegetal pole and does not bisect the egg equally into two blastomeres,the plane of cleavage is:

Identify $A$ and $B$ and their respective functions:

$A$: In the morula stage,the cells divide without any increase in size.
$R$: The zona pellucida remains intact until cleavage is completed.

Fertilization is the fusion of:

In human female,the blastocyst