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
Self etching primers 
Select and explain. 
A. Simultaneously etch and prime dentin and enamel, B. Etches enamel only, C. Only bonds to enamel, D. Only removes smear layer
A: Simultaneously etch and prime dentin and enamel
Answer: A: Simultaneously etch and prime dentin and enamel 
Explanation: None