Question

mary has type a blood. her son bill has type ab blood. which blood type does bills dad have if he is homogenous for blood type?
a
b
ab
o

Explanation:

Blood - type inheritance is determined by alleles. Mary has type A blood, which can have genotypes AA or AO. Bill has type AB blood. Since Bill has a B - allele which Mary doesn't have, and Bill's dad is homogenous, the dad must have type B blood (genotype BB) to pass on the B - allele to Bill.

Answer:

B. B