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': 'Estimation of S. Ca2+ should be done only after- \nSelect and explain. \nA. Urine calcium, B. Total plasma protein, C. S. Phosphate, D. S.K+', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans is options 2 and 3 Factors affecting serum Calcium are Amount of protein present in blood pH of blood Ref Ganong 21/e p385', 'role': 'assistant'}]