In vitro fertilization (IVF) is defined as:

• A. Uniting of egg and sperm inside the woman's body.
• B. Uniting of egg and sperm in a laboratory dish, outside the body.
• C. Fertilizing an egg with donor sperm naturally.
• D. Producing twins through embryo splitting.

Answer: (B)

IVF means fertilizing an egg with sperm in a laboratory dish, outside the body. The term "in vitro" means "in glass," signaling that fertilization happens in a controlled lab setting rather than inside the woman’s reproductive tract. After the embryo forms, it is cultured and then transferred into the uterus for implantation. The other descriptions describe fertilization inside the body, natural fertilization with donor sperm, or embryo splitting to make twins, none of which define IVF.