Answer:
Option C
So, for them to be able to produce an O type (genotype OO) child (Gregory), Both Irene and William have one copy each of O trait to be able to give birth to Gregory.
Step-by-step explanation:
If Irene's bloodtype is A, her genotype could be either AO or AA. Since Williams does not know his bloodtype but knows his parents were both B which could be BO or BB. It is safe to assume that Williams could be a BO if is parents were BO and BB for him to produce a child with O type with Irene.
So, for them to be able to produce an O type (genotype OO) child, each has one copy each of O trait to give birth to Gregory.