Which of the following best defines in vitro fertilization?

• A. Cloning
• B. The union of egg and sperm
• C. Fertilization taking place outside a woman's body
• D. The fusion of egg and cell nucleus

Answer: (C)

In vitro fertilization is defined by fertilization happening outside the woman’s body. The term in vitro means in a lab dish, so eggs are retrieved and fertilized with sperm in a controlled lab setting, and the resulting embryos are then placed into the uterus for implantation. This distinguishes IVF from natural conception, which occurs inside the body.

Cloning is a different process entirely, involving creating a genetic copy rather than combining egg and sperm. Simply stating the union of egg and sperm describes fertilization in general, which can occur inside the body (natural conception) as well as outside the body in IVF, but the defining feature of IVF is that the fertilization takes place outside the body. The idea of merging an egg with a cell nucleus is associated with cloning techniques, not the standard IVF process.