Embryonic stem cells have shown promise when used to treat certain diseases. Despite this, there are many people opposed to stem cell research based on ethical grounds. What is one of their concerns?
A) Embryonic stem cell research is too expensive to pursue.
B) Embryonic stem cell research requires the use of human embryos.
C) Embryonic stem cell research has resulted in no positive effects.
D) Embryonic stem cell research requires the creation of human embryos.