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: Pathology
All the following affects absorption of calcium, EXCEPT 
Select and explain. 
A. Citric acid, B. Retinoic acid, C. Phytates, D. Oxalates
B: Retinoic acid
Answer: B: Retinoic acid 
Explanation: None