Answer:
The correct answer would be 1) a person with AB blood type.
Codominance is the condition in which both the alleles of the gene express themselves completely in the heterozygous condition.
AB blood group can be a perfect example of the codominance. Both the alleles (A and B) express themselves completely and lead to the formation of protein A (or antigen A) and protein B (antigen B) on the surface of the red blood cells.