This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
[{'content': 'Most useful investigation in diagnosis of diabetic ketoacidosis - \nSelect and explain. \nA. Ketonemia, B. pH of blood, C. Urinary sugar, D. Urine ketone', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref - semantischolar.org', 'role': 'assistant'}]