In the Context of Making an Estimate of the Relative

In the context of making an estimate of the relative influence of genes and environment on a trait, identify a true statement about family studies.

A) Researchers study twins that are raised in either their biological family or an adoptive family.
B) Researchers measure the degree to which biological relatives share certain traits.
C) Researchers look at similarities between adopted children and their adoptive families.
D) Researchers compare pairs of monozygotic, or identical, twins with same-sex dizygotic, or fraternal, twins.