<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 60-year-old man comes to the emergency department because of recurrent episodes of fatigue, palpitations, nausea, and diaphoresis over the past 6 months. The episodes have become more frequent in the last 2 weeks and he has missed work several times because of them. His symptoms usually improve after he drinks some juice and rests. He has had a 2-kg 4.5-lb weight gain in the past 6 months. He has a history of bipolar disorder, hypertension, and asthma. His sister has type 2 diabetes mellitus and his mother has a history of medullary thyroid carcinoma. His medications include lithium, hydrochlorothiazide, aspirin, and a budesonide inhaler. His temperature is 36.3C 97.3F, pulse is 92min and regular, respirations are 20min, and blood pressure is 11865 mm Hg. Abdominal examination shows no abnormalities. Serum studies show:Na 145 mEqLK 3.9 mEqLCl- 103 mEqLCalcium 9.2 mgdLGlucose 88 mgdLWhich of the following is the most appropriate next step in diagnosis?? A: Oral glucose tolerance test, B: 24-hour urine catecholamine test, C: 72-hour fasting test, D: Water deprivation test, E: Corticotropin stimulation test,  <response>: This is a question about a 60-year-old man with recurrent episodes of fatigue, palpitations, nausea, and diaphoresis that have been worsening over the past 6 months. The key findings in the history and physical exam are episodes of symptoms that improve after drinking juice and resting, weight gain, and family history of endocrine disorders. The lab results show normal sodium, potassium, chloride, calcium, and glucose. This presentation is most consistent with hypoglycemia, likely due to an insulinoma given the episodic symptoms that improve with carbohydrate intake. An insulinoma is a tumor of the pancreatic beta cells that secretes excess insulin, leading to hypoglycemia. The next best step in diagnosis would be to document hypoglycemia during an episode of symptoms, which can be done with a 72-hour fasting test.C: 72-hour fasting test 