You are answering a USMLE-style medical question. Question: A group of investigators is studying the association between a fire retardant chemical used on furniture and interstitial lung disease. They use hospital records to identify 50 people who have been diagnosed with interstitial lung disease. They also identify a group of 50 people without interstitial lung disease who are matched in age and geographic location to those with the disease. The participants' exposure to the chemical is assessed by surveys and home visits. Which of the following best describes this study design? Options: A) Case-control study B) Case series C) Retrospective cohort study D) Randomized controlled trial Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.