To solve this problem, we need to understand the process of IVF (In Vitro Fertilization) and the stages at which transfers occur.$\newline \bullet$IVF involves fertilizing an ovum outside the body and then transferring the resulting zygote or embryo back into the female reproductive tract.$\newline \bullet$Option 1: Ovum into the fallopian tube - This is not part of the IVF process. Instead, this is related to GIFT (Gamete Intrafallopian Transfer).$\newline \bullet$Option 2: Zygote into the fallopian tube - This is known as ZIFT (Zygote Intrafallopian Transfer), where the zygote is transferred into the fallopian tube. This is a part of IVF.$\newline \bullet$Option 3: Zygote into the uterus - This is not typically done in IVF. Instead, embryos are transferred into the uterus.$\newline \bullet$Option 4: Embryo with 16 blastomeres into the fallopian tube - This is not a standard practice in IVF. Embryos are usually transferred into the uterus.$\newline$Therefore, the correct option is Option 2: Zygote into the fallopian tube.