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
Radio-luscent renal stones are composed of -a) Cysteineb) Calcium phosphatec) Uric acidd) Xanthine 
Select and explain. 
A. cd, B. bc, C. bd, D. ac
A: cd
Answer: A: cd 
Explanation: None