Read the given passage and answer the question.

ABO blood groups in human beings are controlled by the gene $I$. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene ($I$) has three alleles $I^A, I^B$ and $i$. The alleles $I^A$ and $I^B$ produce a slightly different form of the sugar while allele $i$ does not produce any sugar. Because humans are diploid organisms, each person possesses any two of the three $I$ gene alleles. $I^A$ and $I^B$ are completely dominant over $i$.

The number of phenotypes in ABO blood groups is :

4

The correct answer is Option (2) → 4

Human blood group inheritance is an example of both codominance and multiple alleles. It is controlled by three alleles:, I^A , I^B and i . The I^A and I^B alleles exhibit codominance, while the i allele is recessive to both I^A and I^B .There are six possible genotypes: I^AI^A , I^A i , I^B I^B ,I^B i , I^AI^B and ii .

Because I^A and I^B are dominant over the i allele, the genotypes I^A i and I^B i result in A and B blood groups, respectively. The genotypes I^AI^A, I^B I^B , and i i correspond to A, B, and O blood groups, respectively. Due to the codominance of I^A and I^B, the I^AI^B genotype produces the AB blood group. Thus, these six genotypes result in four different phenotypes. Consequently, parents with A and B blood groups can have children with A, B, AB, or O blood groups. The correct answer is "A".