<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 54-year-old man presents to his primary care physician for back pain. His back pain worsens with standing for a prolonged period of time or climbing down the stairs and improves with sitting. Medical history is significant for hypertension, type II diabetes mellitus, and hypercholesterolemia. Neurologic exam demonstrates normal tone, 55 strength, and a normal sensory exam throughout the bilateral lower extremity. Skin exam is unremarkable and dorsalis pedis and posterior tibialis pulses are 3. Which of the following is the best next step in management?? A: Ankle-brachial index, B: MRI of the lumbosacral spine, C: Naproxen, D: Radiography of the lumbosacral spine, E: Surgical spinal decompression,  <response>: This is a patient with back pain that worsens with prolonged standing or going down stairs, which improves with sitting. The history and physical exam findings are consistent with neurogenic claudication from lumbar spinal stenosis. The choices include diagnostic tests like ankle-brachial index, MRI, radiography, and treatments like naproxen and surgery. The best initial step would be a non-invasive imaging test to evaluate for spinal stenosis before considering treatments. Ankle-brachial index is used to evaluate peripheral arterial disease, which is less likely based on the 3 pedal pulses. Naproxen and surgery would be premature before confirming the diagnosis. MRI provides better visualization of the neural elements compared to plain radiography, and is the best choice for initial imaging.B: MRI of the lumbosacral spine 