Question

A women with type A blood claims that man type AB blood is father of child who is type B blood.
Could this man be the father of the child?

Answer 1

assuming he's the father, what must the mother's genotype be?

Answer 2

If a woman has type A blood, her genotype could be AA or AO. If a man has type AB blood, his genotype must be AB.

If the mother is AA, the offspring genotypes could be AA or AB.
If the mother is AO, the offspring genotypes could be AA, AB, AO, or BO.

Do any of these options give you a child with type B blood?