Comparisons Between the Correlations of Intelligence Scores in Identical and Fraternal

Comparisons between the correlations of intelligence scores in identical and fraternal twins are often regarded as evidence for the role of genetic factors in the development of intelligence. This argument is based on the assumption that __________.

A) siblings have shared genes and shared environments
B) identical twins have the same phenotype
C) fraternal twins have the same genotype and different phenotypes
D) the environments of identical twins are no more similar than those of fraternal twins