Final answer:
No, it's not possible for a couple both with blood type O to have a baby with blood type B, as blood type is determined by parental genes.
Step-by-step explanation:
According to the inheritance pattern of ABO blood types, it is not possible for a couple who both have blood type O (genotype ii) to have a child with blood type B. The gene that determines blood type is passed down from parents to their offspring. In this case, both parents have the i allele, which only produces blood type O. Blood type B requires the presence of the IB allele. Therefore, the couple can only have children with blood type O, and not blood type B.