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
Highest bond strength is of: 
Select and explain. 
A. 4th generation DBA., B. 5th generation DBA., C. 6th generation DBA., D. 7th generation DBA.
A: 4th generation DBA.
Answer: A: 4th generation DBA. 
Explanation: None