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
Most useful investigation in diagnosis of diabetic ketoacidosis - 
Select and explain. 
A. Ketonemia, B. pH of blood, C. Urinary sugar, D. Urine ketone
A: Ketonemia
Answer: A: Ketonemia 
Explanation: Ref - semantischolar.org