Why are immune cells extracted from umbilical cord blood better for transplantation ?

As much as I oppose doing other people's hw... the answer is d. The biology is a bit over my head (I know because I had the transplant with cord blood), but I where they have to match the antigens, babies have fewer antigens or something like that than adults. Because of that, they can mismatch donor and recipient far more than what they can with an adult donor (they want adult donors to be a near perfect match, but the cord blood used in my transplant was only a 6 out of 10 match), but the chances of rejection and gvhd are less.