A parent with AB blood could not produce a child type?

A parent with AB blood could not produce a child with O blood.

A person with AB blood has both A and B antigens on their red blood cells, and neither anti-A nor anti-B antibodies in their plasma. To produce a child with O blood, the child would have to inherit an O allele from both parents. However, a parent with AB blood can only pass on A or B alleles, so they cannot produce a child with O blood.