In Twin Studies, Scientists Measure Concordance, Which Is Defined as The

In twin studies, scientists measure concordance, which is defined as the:

A) extent to which variation in phenotype in a population is due to variation in genotype.
B) percentage of cases in which both members of a pair of twins show the trait when at least one member shows it.
C) percentage of cases in which both members of a pair of identical twins, but not fraternal twins, show the trait when at least one member shows it.
D) percentage of cases in which both members of a pair of fraternal twins, but not identical twins, show the trait when at least one member shows it.
E) extent to which differences in the environment influences differences in phenotype.