Infertility is believed to be due to the lack of which vitamin?

$A$: Inability to conceive or produce children even after $2$ years of unprotected sexual cohabitation is called infertility.
$R$: Infertility is a synonym for sterility.

Which of the following methods involves $In \, vivo$ fertilization?

Which of the following techniques is adopted in the test-tube baby program?

In which technique is the embryo,up to the $8$-celled stage,transferred into the fallopian tube of the mother or a surrogate mother?

Test tube babies are produced by