C. 50%
Step-by-step explanation:
- The woman has blood group O so her genotype will be
. - The husband has blood group A so his genotype could either be
. - Since the husband's father was having blood group B so it is obvious that the husband is heterozygous with genotype
. - A cross between heterozygous dominant and homozygous recessive is a test cross and will yeild 50% offspring with recessive genotype.
- So the probability of the child having blood group O is 50%.