In codominance, heterozygote (Aa) has an intermediate phenotype between the dominant homozygote (AA) and recessive homozygote (aa).

For an AD disease, only 80% of individuals with heterozygote genotypes actually develop the disease symptoms. This indicates that A: penetrance of this disease is 80%. B: penetrance of this disease is 20%. C: expressivity of this disease is 80%. D: expressivity of this disease is 20%.