What’s the blood type of a child whose parents are both type O?

If both parents have type O blood, the child must have type O blood.
ABO blood type is a type based on the red blood cell membrane antigens A and B. For example, if there is only antigen A on the cell membrane, it belongs to blood type A. If there is only antigen B, it belongs to blood type B, and if there is only antigen B, it belongs to blood type O, it represents that there are no both antigens on the cell membrane.
If both parents have blood type O, both parents do not have antigen A and antigen B on their red blood cell membranes, and the inheritance of blood type takes place through the chromosomes in the cells.A and B are dominant, while O is recessive, so two parents with blood type O can only give birth to children with blood type O, and they do not have antigens A and B on their cell membranes either.
Therefore, if both parents have O blood type, the child must have O blood type.