$A$ woman who substitutes or takes the place of the real mother to nurse the embryo is called

The first case of $IVF-ET$ technique success was reported by:

$A$: In test-tube baby programme,ova from wife/donor (female) and sperms from the husband/donor (male) are collected and induced to form zygote under simulated conditions in laboratory.
$R$: Embryos with more than $8$ blastomeres are then transferred to fallopian tube $(ZIFT)$ to complete its further development.

If a person is suffering from severe male infertility due to very few sperms (oligozoospermia) or even no live sperms (azoospermia) in the ejaculate,it can be overcome by . . . . . . . This should offer couples an alternative to using donor sperm.

In which technique does fertilization occur inside the body of the female?

Cryopreservation of gametes can be done at $...............$.