Aman with type a blood marries a woman with type
b. their offspring all have type ab blood. the pattern of inheritance is called

The pattern of inheritance is called codominance when the father has type A and the mother has type B and the kids have type AB blood. This is when the both of the alleles will show equal dominance/impact after mating. The type A blood has the gene pattern iAi or iAiA. The type B blood has the gene pattern iBi or iBiB. The correct answer to this question is "codominance."