, ABO blood grouping is controlled by the gene I, which has three alleles: , , and . and are dominant over .

• Child Analysis: The child is Blood Group A. Possible genotypes are or . Since the father is Blood Group B (genotypes or ), he does not possess the allele to pass on. Therefore, the child cannot be . The child must be , having received from the mother and from the father.
• Father Analysis: For the father to contribute an allele while being Blood Group B, his genotype must be .
• Mother Analysis: The mother is Blood Group A and contributes the allele. Her genotype can be or .
• Conclusion: Option B fits this logic: Mother () contributes , Father () contributes , resulting in a Child () with Blood Group A.