Answer: The chances that the baby will have type O is 25%
Explanation: Both the male and female are heterozygous for type B blood, this means that they both have one dominant allele for type B blood and one recessive allele for type O blood. Remember that in the ABO blood system, The alleles for type A and B are dominant while the allele for type O blood is recessive.
This means that the genotypes of both parents for type B blood is BO.
BO x BO = BB, BO, BO, and OO.
Phenotypically, BB and BO will manifest as type B blood while OO will manifest as type O blood.
From the cross between the two parents, one out of the four offsprings has type O blood, therefore the chances of a child having type O blood is 1/4 x 100 = 25%.
See the attached punnet square for further information