<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 72-year-old male with a past medical history significant for aortic stenosis and hypertension presents to the emergency department complaining of weakness for the past 3 weeks. He states that, apart from feeling weaker, he also has noted lightheadedness, pallor, and blood-streaked stools. The patients vital signs are stable, and he is in no acute distress. Laboratory workup reveals that the patient is anemic. Fecal occult blood test is positive for bleeding. EGD was performed and did not reveal upper GI bleeding. Suspecting a lower GI bleed, a colonoscopy is performed after prepping the patient, and it is unremarkable. What would be an appropriate next step for localizing a lower GI bleed in this patient?? A: Nasogastric tube lavage, B: Technetium-99 labelled erythrocyte scintigraphy, C: Ultrasound of the abdomen, D: CT of the abdomen, E: Flexible sigmoidoscopy,  <response>: This is a question about the appropriate next step to localize a lower GI bleed in a 72-year-old male patient with a history of aortic stenosis and hypertension. The patient presents with weakness, lightheadedness, pallor, and blood-streaked stools over 3 weeks. He is anemic and has a positive fecal occult blood test, but EGD and colonoscopy were unremarkable. The choices given are diagnostic tests that could potentially identify the source of bleeding in the lower GI tract. To select the best answer, we need to consider which test would be most appropriate and effective for localizing an obscure source of lower GI bleeding after upper endoscopy and colonoscopy have failed to identify the cause.B: Technetium-99 labelled erythrocyte scintigraphy 