You are conducting a study on the health of people who have been exposed to radiation and those who have not been exposed to radiation. which of these methods of obtaining data should you most likely adopt and why?

a. an observational study because it involves the pre-existing condition of the subjects
b. an experimental study because it will give the most accurate results
c. an experimental study because results can be obtained much faster using this technique
d. a sample survey with only people who were not exposed to radiation because it involves random selection
e. a sample survey with only people who were exposed to radiation because it involves random selection