Why do researchers find the study of fraternal twins important?

a. They share similar environments and the same genetic code.

b. Data collected concerning their similarities is necessary for calculating heritability.

c. They are the same age and are usually raised in similar environments, but they do not have the same genetic code.

d. Results allow us to determine exactly how disorders ranging from heart disease to schizophrenia are inherited.

e. They are typically raised in less similar environments than nontwin siblings.