To solve this problem, we need to identify the characteristics that represent the inheritance of blood groups in humans. Let's analyze each characteristic:$\newline \bullet$a. Dominance:$\newline$ - In the ABO blood group system, the A and B alleles are dominant over the O allele.$\newline$ - This means that if an individual inherits an A or B allele along with an O allele, the phenotype will be A or B, respectively.$\newline \bullet$b. Co-dominance:$\newline$ - The A and B alleles are co-dominant, meaning that if an individual inherits both alleles, the phenotype will be AB, expressing both antigens.$\newline \bullet$c. Multiple allele:$\newline$ - The ABO blood group system is controlled by a single gene with three alleles: A, B, and O.$\newline$ - This is an example of multiple alleles, where more than two alleles exist for a particular gene.$\newline \bullet$d. Incomplete dominance:$\newline$ - Incomplete dominance is not applicable to the ABO blood group system, as it involves blending of traits, which does not occur here.$\newline \bullet$e. Polygenic inheritance:$\newline$ - Polygenic inheritance involves multiple genes contributing to a single trait, which is not the case for the ABO blood group system.$\newline$Based on the analysis, the characteristics that represent the inheritance of blood groups in humans are:$\newline$a. Dominance, b. Co-dominance, and c. Multiple allele.$\newline$Therefore, the correct option is Option 2: a, b, and c.