A man with blood group A marries a woman with blood group AB. Which amongst the following cannot be the blood group of the offspring?

If a man with blood group A marries a woman with blood group AB. Then the genotype of the man can be IAIA or IAi. The woman will have genotype IAIB. When  IAIA  is crossed with IAIB. Then the offspring will have blood group A or blood group AB. When  IAi  is crossed with IAIB, then the offspring can have genotype of A, B or AB. But in either of the cases O blood group is not possible.