Twin Studies Have Been Used to Assess the Relative Importance

Twin studies have been used to assess the relative importance of "nature" versus "nurture" in determining variation among individuals for complex traits. Which of the following statements is TRUE?

A) Identical twins differ because of genotype and environment.
B) Fraternal twins differ only because of environment.
C) Twin studies show that autism and clinical depression are significantly influenced by genotype.
D) The concordance of fraternal twins is greater than that of identical twins for most complex traits.
E) Studies of fraternal twins compensate for environmental influences that may be stronger for identical twins compared to fraternal twins.