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
Anterior - posterior spread of implant is: 
Select and explain. 
A. Distance from center of most anterior implant to the center of most posterior implant, B. Distance from center of most anterior implant to the distal surface of most posterior implant, C. Distance from distal surface of most anterior implant to the mesial surface of most posterior implant, D. Distance from mesial surface of most anterior implant to the distal surface of most posterior implant
B: Distance from center of most anterior implant to the distal surface of most posterior implant
Answer: B: Distance from center of most anterior implant to the distal surface of most posterior implant 
Explanation: None