Can a O mom produce child with ab dad?

No, a person with O blood type cannot produce a child with AB blood type, regardless of the blood type of the father.

Blood type is determined by the presence or absence of certain antigens on the surface of red blood cells. There are four main blood groups: A, B, AB, and O. People with AB blood type have both A and B antigens on their red blood cells, while people with O blood type do not have either A or B antigens.

When a person with AB blood type has a child with a person with O blood type, the child can only inherit either A or B antigens, not both. This means that the child can only have A blood type or B blood type, but not AB blood type.