Final answer:
Heritability (H) would be equal to 1.0 if a disorder is entirely due to genetic factors, indicating that all variation in the trait is due to genetic differences with no influence from environmental factors.
Step-by-step explanation:
If the heritability (H) of a disorder is entirely due to genetic factors, then H would be equal to 1.0 (D). Heritability is the fraction of phenotype variation that can be attributed to genetic differences among individuals within a population. When heritability is 1.0, it indicates that all variation in the trait can be attributed to genetic variation. This means that environmental factors do not contribute to the phenotypic variation of that trait within the population.