The blood groups with both homozygous and heterozygous genotypes are ___.

The correct option is C

A & B

Blood group A has two genotypes $I^A{I}^A$ which is homozygous and $I^A{I}^O$ which is heterozygous. Similarly, blood group B has two genotypes $I^B{I}^B$ which is homozygous and $I^B{I}^O$ which is heterozygous.
Blood group AB is always heterozygous with the genotype $I^A{I}^B$ and blood group O is always homozygous, and its genotype is represented as $I^O{I}^O$ or ii.