So to form blood type AB, the male parent has to be A. The female parent has to be B, or vice versa. This male has to be B, and this female has to be A. And only then will we form blood type AB. And finally, to form blood type O, both of these have to be recessive, meaning they both have to lack these genes that code for either one of these antigens. And so in that case, if we have recessive and recessive, we form lowercase IO, lowercase IO, and that gives us blood type O.