<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 36-year-old man comes to the physician because of increasing back pain for the past 6 months. The pain is worse when he wakes up and improves throughout the day. He has problems bending forward. He has taken ibuprofen which resulted in limited relief. His only medication is a topical corticosteroid for two erythematous, itchy patches of the skin. His mother has rheumatoid arthritis. His temperature is 37.1C 98.8F, pulse is 75min, respirations are 14min, and blood pressure is 12682 mmHg. Examination shows a limited spinal flexion. He has two patches with erythematous papules on his right forearm. He has tenderness on percussion of his sacroiliac joints. An x-ray of his spine is shown. Which of the following is most likely to improve mobility in this patient?? A: Leflunomide, B: Etanercept, C: Methotrexate, D: Prednisolone, E: Rituximab,  <response>: This is a patient with back pain and limited spinal flexion on exam, suggesting an inflammatory spondyloarthropathy. He also has sacroiliac joint tenderness and skin findings consistent with psoriasis, further supporting this diagnosis. The x-ray shows sacroiliitis, confirming the diagnosis of ankylosing spondylitis. The question asks which medication is most likely to improve mobility in this patient. Ankylosing spondylitis is typically treated with TNF-alpha inhibitors like etanercept to reduce inflammation and improve mobility. Methotrexate can also be used but is less effective than TNF inhibitors. Leflunomide, prednisolone, and rituximab are not first-line treatments.B: Etanercept 