<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 16-day-old male newborn is brought to the emergency department because of fever and poor feeding for 2 days. He became very fussy the previous evening and cried for most of the night. He was born at 36 weeks gestation and weighed 2430 g 5 lb 3 oz. The pregnancy and delivery were uncomplicated. The mother does not recall any sick contacts at home. He currently weighs 2776 g 6 lb 2 oz. He appears irritable. His temperature is 38.6C 101.5F, pulse is 180min, and blood pressure is 8251 mm Hg. Examination shows scleral icterus. He becomes more agitated when picked up. There is full range of motion of his neck and extremities. The anterior fontanelle feels soft and flat. Neurologic examination shows no abnormalities. Blood cultures are drawn and fluid resuscitation is initiated. A urinalysis obtained by catheterization shows no abnormalities. Which of the following is the most appropriate next step in diagnosis?? A: MRI of the head, B: Reassurance, C: Urine culture, D: CT scan of the head, E: Lumbar puncture,  <response>: This is a clinical vignette about a 16-day-old male newborn infant presenting with fever, poor feeding, irritability, and crying. Important findings include the infants gestational age, birth weight, current weight, vital signs showing tachycardia, physical exam showing scleral icterus, and a normal urinalysis. The main differential diagnosis is between a serious bacterial infection like meningitis vs a more benign cause like a viral illness. Imaging like CT or MRI could be helpful to rule out abnormalities but a lumbar puncture would be the most appropriate next step to analyze the CSF and determine if there is an infection like meningitis. Reassurance or urine culture would not be the best next step.E: Lumbar puncture 