听力原文：Stem cells are undeveloped human cells that can grow into many or all of the different specialized cells in the human body. Although stem cells have been harvested from adults, the most versatile stem cells come from embryos. The main source of embryos is fertility clinics. Vitro fertilization, the process that produces test-tube babies, involves the fertilization of eggs to produce embryos outside the woman's body. Which of the following statements is NOT true of the passage?