And so when we cross, we get X uppercase B, lowercase BX, uppercase BX, lowercase B, and right away we should see that that's a problem. And that's a problem because we form this female right over here. So according to the pedigree, we have this female individual that contains both lowercase B's on both of those X chromosomes. But in this particular Punnett square, we see that is impossible because 100% of those females must be heterozygous and so they must express that disease, that phenotype, and that is inconsistent with this particular information. And so it cannot be sex link dominant. So he basically answered our question.