When the incidence of a disease in adopted children is studied and compared with its incidence in biologic relatives and in adoptive relatives, all of the following are relevant concerns except:
a. Age at onset
b. Amount of contact maintained by the adoptee with his or her biologic parents
c. Marital status of the biologic parents
d. Selection factors relating to who is adopted and who is not
e. c and d
Answer: c. Marital status of the biologic parents