Punnett Square for ABO Inheritance

Steps:

• Mother's genotype is I^A I^A (homozygous A), so all gametes carry I^A.
• Father's genotype is I^B i (heterozygous B), so gametes are 50% I^B and 50% i.
• Offspring genotypes: I^A I^B (AB blood type) or I^A i (A blood type).
• No O (ii) or homozygous B possible from this cross.

Why B is correct:

• Mendelian inheritance from I^A I^A × I^B i yields only I^A I^B (AB) and I^A i (A) phenotypes.

Why the others are wrong:

• A: Excludes AB, which forms from I^A and I^B alleles.
• C: Includes O (ii), but no i allele from mother prevents ii genotype.
• D: Includes O (impossible) and redundantly lists A, B, AB.

Final answer: B