Answer:
Woman's genotype is AO
Man's genotype is BO
Explanation:
For a woman with blood group A and a man with blood group B to give birth to a child with blood group O. Their genotypes will be:
Woman's genotype is AO
Man's genotype is BO
The can have a child with blood group A, B, AB and O
1/4 will have type AB blood group;
1/4 will have AO, which is type A blood group;
1/4 will have BO, which is type B blood group;
1/4 will have OO, which is type O blood group