A person is either AB or B or A or O group. At the same time they are ALSO rhesus neg. Or thesus pos. ((PLUS many other too )But usually blood grouping refers to the ABO system and the Rhesus group. So AB can be AB pos or AB neg as can also B and A and O . O is always oo and can only pass on o . AB can pass on their A and their B. But groups A and B can be AA or Ao and BB or Bo . A and B are co dominant so that if you inherit both you are AB type. O is recessive. So if you are Ao or Bo you are still A group or B group but a carrier of o in both these cases. Groups AA can only pass on
A and BB can only pass on B .
A and BB can only pass on B .