Studies Comparing the Similarity of Identical and Fraternal Twins Who

Studies comparing the similarity of identical and fraternal twins who are raised together and apart are especially informative because:

A) they tell us only about the importance of the environment.
B) they tell us about the relative importance of the environment and genetic factors.
C) they tell us what genes may be responsible for the occurrence of twins.
D) they tell us only about the importance of genetic factors.