This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: New Born Infants, Subject name: Pediatrics
[{'content': 'A very preterm baby on 30 mL/kg of enteral feeding developed sudden severe abdominal distension with visible bowel loops on day 6 of life. The baby also showed temperature instability and lethargy. X-ray of the abdomen showed portal venous gas. The staging of NEC is? \nSelect and explain. \nA. I, B. 2a, C. 2b, D. 3a', 'role': 'user'}, {'content': "Answer: C \nExplanation: c. 2b(Ref: Nelson's 20/e p 869-870, Ghai 8/e p 165-166)Stage of NECRadiological featureINormal/mild intestinal dilatation IIIIa: Pneumatosis intestinalis;IIb: Portal vein gasIIIIIIa: Peritonitis/Ascites;IIIb: Pneumoperitoneum", 'role': 'assistant'}]