This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pediatrics
[{'content': 'The metabolic dearrangement in congenital pyloric stenosis is \nSelect and explain. \nA. Hypochloremic alkalosis, B. Hyperchloremic alkalosis, C. Hyperchloremic acidosis, D. Hypochloremic acidosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The classical presentation is non bilious vomiting begining at 3-6 weeks of age Severity and frequency of vomiting increases gradually Persistant vomiting leads to malnutrition,dehydration and hypochloremic alkalosis. constipation is usual Diagnosis is based on history and palpability of mass. Ref : ESSENTIAL PEDIATRICS,O.P.GHAI,PG NO:253,7 th edition', 'role': 'assistant'}]