Among the following pairs, choose the couple whose offspring have the blood group of neither of the parents.
I. A X O                                                            II. AB X O 
III. B X AB                                                        IV. Homozygous A X homozygous B
 

Off spring of the couple with the blood groups AB and O have either A or B as their blood group. Off spring of couple with blood groups homozygous for A and B will have the offspring with blood group AB. Offspring of couple with A and O blood group have either A or both A and O. Similarly couple with B and AB groups have offspring with either B or AB or A.