Why Is IUI More Likely to Result in Multiple Births

Why is IUI more likely to result in multiple births than IVF?

A) During IUI,one fertilized egg is split to produce multiple embryos.
B) During IUI,semen is injected directly into the uterus.
C) During IVF,only one embryo is injected into the uterus at a time.
D) During IVF,only one egg is harvested from the ovary at a time.
E) During IUI,multiple embryos are injected into the uterus at one time.