In 2019, scientists conducted a research study about spicy food as a potential risk factor for gastroesophageal reflux disease (GERD). Scientists enrolled 500 patients with GERD. An additional 1,000 persons without GERD were also enrolled, matched on gender to patients with GERD. Participants self-reported their recent spicy foods consumption. What study design did the scientists use to answer their research question? a. Case-control study b. Cross-sectional study c. Prospective cohort study X d. Randomized clinical trial X.