Answer: 0%
Explanation: In the ABO blood type, blood types are classified based on the antigens present in the red blood cells. The antigens that are found in the red blood cells are of two types: A antigens and B antigens.
In blood grouping, blood type A contains A antigens, blood type B contains B antigens, blood type AB contains A and B antigens while blood type O has neither A nor B antigens.
These blood groups are controlled by two alleles (a pair of gene). If a woman with type O blood marries a man who is heterozygous for blood type B, none of the children will have blood type AB not even the first child because each child will inherit one allele from each parent.
Therefore, since neither the woman nor the man has antigen A in their system then none of the children will have blood type AB. For an individual to have blood type AB, he must have inherited antigens A and B, one from each parent.
This implies that the probability that the first child will have AB blood type is 0%.
