Which technique allows fertilization to occur outside the body?

The technique that allows fertilization to occur outside the body is in vitro fertilization (IVF). IVF involves the process where eggs are retrieved from a woman's ovaries and fertilized by sperm in a laboratory setting. This allows for the precise control of the fertilization process, as environmental conditions can be optimized for egg and sperm viability. After fertilization, the resulting embryos can then be cultured for several days before being implanted into the uterus, which increases the chances of successful pregnancy.

Nuclear transfer is a cloning technique that involves transferring the nucleus of a somatic cell into an egg cell that has had its nucleus removed. While it involves manipulating embryos, it does not specifically facilitate fertilization outside the body in the context of traditional reproductive processes.

Artificial insemination involves placing sperm inside a woman's reproductive tract via a medical procedure, which typically occurs within the body, rather than allowing for fertilization in a controlled external environment.

Gene editing refers to various techniques used to alter the genetic material of an organism, which does not pertain to the process of fertilization at all. Therefore, IVF stands out as the only method directly focused on achieving fertilization externally.