<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 43-year-old woman visits her primary care physician complaining of abdominal pain for the past 6 months. She reports that the pain is localized to her lower abdomen and often resolves with bowel movements. She states that some days she has diarrhea while other times she will go 4-5 days without having a bowel movement. She started a gluten-free diet in hopes that it would help her symptoms, but she has not noticed much improvement. She denies nausea, vomiting, hematochezia, or melena. Her medical history is significant for generalized anxiety disorder and hypothyroidism. Her father has a history of colon cancer. The patient takes citalopram and levothyroxine. Physical examination reveals mild abdominal tenderness with palpation of lower quadrant but no guarding or rebound. A guaiac test is negative. A complete blood count is pending. Which of the following is the next best step in management?? A: Anti-endomysial antibody titer, B: Colonoscopy, C: High fiber diet, D: Loperamide, E: Thyroid ultrasound,  <response>: This is a patient with chronic abdominal pain and irregular bowel habits concerning for irritable bowel syndrome IBS. Key findings include lower abdominal pain relieved by bowel movements, alternating diarrhea and constipation, negative guaiac test, and family history of colon cancer in her father. The choices include tests for celiac disease anti-endomysial antibody, colon cancer screening colonoscopy, dietary changes high fiber diet, symptomatic treatment loperamide, and evaluating her hypothyroidism thyroid ultrasound.In a patient with suspected IBS, colonoscopy is warranted to screen for organic causes like colon cancer, especially with her family history. A high fiber diet may help regulate bowel habits but does not evaluate for underlying pathology. Loperamide treats diarrhea symtpoms but does not evaluate cause. Celiac disease is less likely given lack of improvement on gluten-free diet. Thyroid ultrasound is unrelated to her GI symptoms.B: Colonoscopy 