When the contributions of both alleles are visible in the phenotype like ABO blood groups, the alleles are said to be __ Select one: a. Incomplete dominancy b. Dominant c. Codominant d. Epistasis Clear my choice

The correct answer is c. Codominant.<br /><br />In the ABO blood group system, both alleles contribute to the phenotype. For example, in the case of the AB blood type, both the A and B alleles are expressed, resulting in the presence of both A and B antigens on the surface of red blood cells. This is a classic example of codominance, where both alleles are equally expressed in the phenotype.