Parents with sickle cell anemia in their families ask the nurse to tell them which test for sickle cell anemia can be done the earliest in the prenatal period. The nurse will respond that prenatal diagnosis for sickle cell anemia can be conducted as early as 8 to 10 weeks with which of the following tests?
a. chorionic villi sampling
b. amnionic fluid analysis
c. sickle cell solubility tests
d. hemoglobin electrophoresis