In vitro fertilisation is a technique that involves transfer of which one of the following into the fallopian tube?
1. Embryo only, upto 8 cell stage
2. Either zygote or early embryo upto 8 cell stage
3. Embryo of 32 cell stage
4. Zygote only
Embryo only, upto 8 cell stage
because the embryo is introduced into fallopian tube.