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: Dental
Preferred haemostatic agents for perforation repair include all except? 
Select and explain. 
A. Freeze dried bone, B. Calcium Hydroxide, C. Ferric Sulphate, D. Collagen
C: Ferric Sulphate
Answer: C: Ferric Sulphate 
Explanation: None