<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 62-year-old man comes to the physician because of a 5-day history of fatigue, fever, and chills. For the past 9 months, he has had hand pain and stiffness that has progressively worsened. He started a new medication for these symptoms 3 months ago. Medications used prior to that included ibuprofen, prednisone, and hydroxychloroquine. He does not smoke or drink alcohol. Examination shows a subcutaneous nodule at his left elbow, old joint destruction with boutonniere deformity, and no active joint warmth or tenderness. The remainder of the physical examination shows no abnormalities. His hemoglobin concentration is 10.5 gdL, leukocyte count is 3500mm3, and platelet count is 100,000mm3. Which of the following is most likely to have prevented this patients laboratory abnormalities?? A: Cobalamin, B: Amifostine, C: Pyridoxine, D: Leucovorin, E: Mesnan,  <response>: This is a clinical vignette describing a 62-year-old man with a 5-day history of fatigue, fever, and chills. He has a history of hand pain and stiffness that has worsened over the past 9 months, and he started a new medication for this 3 months ago. His prior medications include ibuprofen, prednisone, and hydroxychloroquine. On exam, he has a subcutaneous nodule, boutonniere deformity, and no active synovitis. Lab tests show anemia, leukopenia, and thrombocytopenia. The question asks which medication could have prevented his abnormal lab results. Based on the history provided, the patient most likely has rheumatoid arthritis that has been treated with various medications including methotrexate the new medication started 3 months ago. Methotrexate can cause myelosuppression, resulting in anemia, leukopenia, and thrombocytopenia. Therefore, the answer is most likely a medication that could prevent myelosuppression from methotrexate.D: Leucovorin 