In the context of blood types, being a heterozygote for type A means that the individual has one A allele and one O allele. Therefore, the correct genotype for a heterozygote A is Ao. This means the individual inherited one A allele from one parent and an O allele from the other parent.
To clarify the other options: AA would indicate a homozygous type A (two A alleles), AB indicates a genotype with both A and B alleles (blood type AB), and BB represents a homozygous type B (two B alleles). Thus, the correct answer is c) Ao.