The possible offsprings of parents with blood groups A $\left({\mathrm{I}}^{\mathrm{A}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}\right)$ and AB $\left({\mathrm{I}}^{\mathrm{A}}\mathrm{ }{\mathrm{I}}^{\mathrm{B}}\right)$ are A, B and AB

	${\mathrm{I}}^{\mathrm{A}}$	${\mathrm{I}}^{\mathrm{O}}$
${\mathrm{I}}^{\mathrm{A}}$	${\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{A}}$ (Blood group A)	${\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group A)
${\mathrm{I}}^{\mathrm{B}}\mathrm{ }$	${\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{B}}$ (Blood group AB)	${\mathrm{I}}^{\mathrm{B}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group B)

Thus in this combination there is B blood group which doesn't match with the parents.

The possible offsprings of parents with blood groups $\mathrm{B}\mathrm{ }\left({\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{O}}\right)$ and $\mathrm{A}\mathrm{B}\mathrm{ }\left({\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{B}}\right)$ are A, B and AB

	${\mathrm{I}}^{\mathrm{B}}$	${\mathrm{I}}^{\mathrm{O}}$
I A	I A I B (Blood group AB)	${\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group A)
${\mathrm{I}}^{\mathrm{B}}$	${\mathrm{I}}^{\mathrm{B}}{\mathrm{I}}^{\mathrm{B}}$ (Blood group B)	${\mathrm{I}}^{\mathrm{B}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group B)

Thus in this combination there is A blood group which doesn't match with the parents.

The possible offsprings of parents with blood groups $\mathrm{O}\mathrm{ }\left({\mathrm{I}}^{\mathrm{O}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}\right)$ and $\mathrm{A}\mathrm{B}\mathrm{ }\left({\mathrm{I}}^{\mathrm{A}}\mathrm{ }{\mathrm{I}}^{\mathrm{B}}\right)$ are A and B

	${\mathrm{I}}^{\mathrm{O}}$
I A	${\mathrm{I}}^{\mathrm{A}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group A)
${\mathrm{I}}^{\mathrm{B}}$	${\mathrm{I}}^{\mathrm{B}}{\mathrm{I}}^{\mathrm{O}}$ (Blood group B)

Thus in this combination there is A and B blood groups which doesn't match with the parents.

The possible offsprings of parents with blood groups $\mathrm{A}\mathrm{ }\left({\mathrm{I}}^{\mathrm{A}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}\right)$ and $\mathrm{O}\mathrm{ }\left({\mathrm{I}}^{\mathrm{O}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}\right)$ are A and O

	${\mathrm{I}}^{\mathrm{O}}$
${\mathrm{I}}^{\mathrm{A}}$	${\mathrm{I}}^{\mathrm{A}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}$ (Blood group A)
${\mathrm{I}}^{\mathrm{O}}$	${\mathrm{I}}^{\mathrm{O}}\mathrm{ }{\mathrm{I}}^{\mathrm{O}}$ (Blood group O)

In this combination there is A and O blood groups which match with the parents.