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
What should be the length of post for posterior teeth: 
Select and explain. 
A. Maximum 7mm below the canal orifice., B. Maximum 5 mm below the canal orifice., C. 2/3 to the root length., D. All of the above.
A: Maximum 7mm below the canal orifice.
Answer: A: Maximum 7mm below the canal orifice. 
Explanation: For anterior teeth post length should be 2/3-3/4of root length.