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
Types of pocket respectively: 
Select and explain. 
A. Simple pocket, compound pocket, complex pocket., B. Simple pocket, complex pocket, compound pocket., C. Compound pocket, simple pocket, complex pocket., D. Simple pocket, compound pocket, tertiary pocket.
A: Simple pocket, compound pocket, complex pocket.
Answer: A: Simple pocket, compound pocket, complex pocket. 
Explanation: None