Researchers identified patients from a community health clinic who came in for routine care between January and December 1988. Patients were all followed for 20 years to determine if they developed cancer; they were put into two groups at study start – those that had an x-ray during that initial 1988 visit and those that didn’t. What study type would this be? a. Prospective cohort b. Retrospective cohort c. Cross-sectional d. Case-control e. Experimental Solution.