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
Working length is 
Select and explain. 
A. 0.5 — 1mm short of radiographic apex, B. 1-2 mm short of radiographic apex, C. Exactly at apex, D. 1-2mm apical to apex
A: 0.5 — 1mm short of radiographic apex
Answer: A: 0.5 — 1mm short of radiographic apex 
Explanation: None