This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Avascular necrosis for patients can be retarded by? 
Select and explain. 
A. 500 mg Ca daily, B. 1000 mg Ca daily, C. 1500 mg Ca daily, D. 2000 mg Ca daily
C: 1500 mg Ca daily
Answer: C: 1500 mg Ca daily 
Explanation: 1500 mg Ca daily REF: Principles and practice of endocrinology and metabolism by Kenneth Becker Page 630 In renal, gastrointestinal or other diseases leading to avascular necrosis, daily calcium supplementation of 1500 mg is required to prevent and reatard avascular necrosis and other metabolic bones diseases.