<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 34-year-old primigravid woman comes to the physician for a prenatal visit at 37-weeks gestation because of worsening back pain for 3 weeks. The pain is worse with extended periods of walking, standing, and sitting. She has not had any changes in bowel movements or urination. Her mother has rheumatoid arthritis. Examination of the back shows bilateral pain along the sacroiliac joint area as a posterior force is applied through the femurs while the knees are flexed. She has difficulty actively raising either leg while the knee is extended. Motor and sensory function are normal bilaterally. Deep tendon reflexes are 2. Babinski sign is absent. Pelvic examination shows a uterus consistent in size with a 37-weeks gestation. There is no tenderness during abdominal palpation. Which of the following is the most likely explanation for this patients symptoms?? A: Spinal cord compression, B: Vertebral bone compression fracture, C: Placental abruption, D: Relaxation of the pelvic girdle ligaments, E: Rheumatoid arthritis,  <response>: This is a medical question asking about the likely explanation for a pregnant womans symptoms of worsening back pain that is worse with walking, standing, and sitting. The key details in the stem are that she is 37 weeks pregnant, has sacroiliac joint tenderness on exam, and has difficulty actively raising her legs when her knees are extended. The choices include spinal cord compression, vertebral fracture, placental abruption, pelvic girdle ligament relaxation, and rheumatoid arthritis. Given that she is late in pregnancy and has sacroiliac joint tenderness and difficulty raising her legs, the most likely explanation is relaxation of the pelvic girdle ligaments, which can occur due to hormonal changes in pregnancy. Spinal cord compression, vertebral fracture, placental abruption, and rheumatoid arthritis are less likely based on the clinical presentation.D: Relaxation of the pelvic girdle ligaments 