In a marriage between male with blood group $A$ and female with blood group $B$, the progeny had either blood group $AB$ or $B$. What could be the possible genotype of parents ?

Parents of blood groups $O$ and $AB$ cannot have a child of group $AB$ because

If a certain patient with blood group $B$ requires immediate blood transfusion, the following type can be given to him

In case of disputed parentage, the blood group analysis of the mother, child and alleged father can

A child's blood group is ‘$O$'. The parents blood groups cannot be