To solve for the answer to this problem, we should first show the genotypes of the blood type of the parents.
Parent 1: O, genotype OO
Parent 2: AB, genotype AB
Now to see to see the possible phenotypes of the offspring, we will do the punnett square:
A AO AO
B BO BO
The baby has a blood type of B (genotype: BB or BO). Therefore the baby can have a blood type of B. But we still have to determine the Rh factor of the baby to know the answer.
Rh+ = genotype: Rh+/Rh+ or Rh+/Rh-
Rh- = genotype: Rh-/Rh-
Since both the parents are Rh-, their baby cannot be Rh+ which is indicated in the problem.
Therefore, it is not possible for a man of blood type AB, Rh- to be the father.
In this case, The baby cannot be having Rh+ blood group..